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Showing 601 - 741 of 741 Journals sorted by number of followers
Quantum Science and Technology     Hybrid Journal   (Followers: 18)
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PNAS Nexus     Open Access   (Followers: 11)
FirePhysChem     Open Access   (Followers: 9)
ImmunoInformatics     Open Access   (Followers: 7)
Environmental Research : Climate     Open Access   (Followers: 7)
Physical Review Fluids     Hybrid Journal   (Followers: 6)
Himalayan Physics     Open Access   (Followers: 6)
Composites Part C : Open Access     Open Access   (Followers: 5)
Sensors International     Open Access   (Followers: 5)
Perspectives of Earth and Space Scientists i     Open Access   (Followers: 4)
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International Journal of Engineering and Applied Physics     Open Access   (Followers: 3)
Physical Review Applied     Hybrid Journal   (Followers: 3)
Results in Surfaces and Interfaces     Open Access   (Followers: 3)
Cell Reports Physical Science     Open Access   (Followers: 2)
Physical Review Research     Open Access   (Followers: 2)
ChemPhysMater     Full-text available via subscription   (Followers: 2)
Magnetic Resonance Letters     Open Access   (Followers: 1)
Chemical Physics Impact     Full-text available via subscription   (Followers: 1)
Jambura Physics Journal     Open Access  
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics     Open Access  
Physics & Imaging in Radiation Oncology     Open Access  
Physics Open     Open Access  
Clinical Spectroscopy     Open Access  

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Physical Review Fluids
Number of Followers: 6  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Online) 2469-990X
Published by APS Homepage  [14 journals]
  • Laser-induced thermocapillary flows on a flowing soap film

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      Authors: Yu Zhao; Haitao Xu
      First page: L022001
      Abstract: Author(s): Yu Zhao and Haitao Xu
      We propose a focused laser heating method to study wave properties of flowing soap films. The laser-induced thermocapillary flows lead to symmetric disturbances in film thickness. The shock waves originating from the propagating symmetric elastic waves, which have remained elusive despite considerable experimental efforts, are thus stimulated on flowing soap films with low surfactant concentrations, or appreciable elasticities. Interestingly, on soap films with high surfactant concentrations, or vanishingly small elasticities, the laser-induced disturbances in film thickness remain unchanged and flow with the film without propagating, creating “laser-engraving” on free liquid films.
      [Phys. Rev. Fluids 9, L022001] Published Thu Feb 08, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, L022001 (2024)
      PubDate: 2024-02-08T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.L022001
      Issue No: Vol. 9, No. 2 (2024)
       
  • Effects of symmetry-breaking mechanisms on the flow field around
           magnetic-responsive material appendages that mimic swimming strokes

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      Authors: Mohammad Mohaghar; Angelica A. Connor, Shuai Wu, Ruike Renee Zhao, Donald R. Webster
      First page: 023101
      Abstract: Author(s): Mohammad Mohaghar, Angelica A. Connor, Shuai Wu, Ruike Renee Zhao, and Donald R. Webster
      This study quantifies the effects of breaking the symmetry of magnetic-responsive material appendage motion. Asymmetry is achieved through distinct shape changes and asymmetric cycle periods. The appendage with an asymmetric joint and asymmetric cycle demonstrates significantly faster downward motion (and enhances swimming efficiency) by reducing the vorticity strength and viscous energy dissipation in the surrounding fluid. The study provides insights into the induced flow and opens avenues for bio-inspired aquatic robots made from magnetic-responsive soft materials with the potential for fostering underwater propulsion and exploration in aquatic environments.
      [Phys. Rev. Fluids 9, 023101] Published Tue Feb 13, 2024
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 9, 023101 (2024)
      PubDate: 2024-02-13T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023101
      Issue No: Vol. 9, No. 2 (2024)
       
  • Stochastic reorientations and the hydrodynamics of microswimmers near
           deformable interfaces

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      Authors: Sankalp Nambiar; J. S. Wettlaufer
      First page: 023102
      Abstract: Author(s): Sankalp Nambiar and J. S. Wettlaufer
      We study the fluid mediated hydrodynamics of an orientable microscopic swimmer that is near a deformable boundary, and that can intrinsically execute random orientation changes. Accounting for swimmer reorientations via orientation tumbles or active Brownian rotations on time scales comparable to the boundary deformations, we find that a pusher-type swimmer can rotate away from the interface, while its attraction towards the interface is enhanced. Depending on the viscosity of the fluids on either side of the interface, the swimmer can experience a stronger migration towards the interface at short times, and away from the interface in the long-time limit.
      [Phys. Rev. Fluids 9, 023102] Published Wed Feb 14, 2024
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 9, 023102 (2024)
      PubDate: 2024-02-14T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023102
      Issue No: Vol. 9, No. 2 (2024)
       
  • Electroosmotic mixing of viscoplastic fluids in a microchannel

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      Authors: Sumit Kumar Mehta; Pranab Kumar Mondal
      First page: 023301
      Abstract: Author(s): Sumit Kumar Mehta and Pranab Kumar Mondal
      This work finds that the yield stress (YS) of electrically actuated viscoplastic fluids significantly influences mixing and aggregation phenomena. When shear force is applied below the YS limit, these fluids exhibit solid-like behavior due to their viscoplasticity. This is commonly observed in biological fluids like blood used in applications where rapid mixing is crucial. The local modulation of electrical forcing is achievable due to the ionic interaction between the solid and liquid phases. This leads to the observation of distinct flow structures, found to be influenced by the YS. Additionally, the likelihood of constituent particles aggregating is strongly correlated with YS.
      [Phys. Rev. Fluids 9, 023301] Published Mon Feb 05, 2024
      Keywords: Complex and Non-Newtonian Fluids
      Citation: Phys. Rev. Fluids 9, 023301 (2024)
      PubDate: 2024-02-05T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023301
      Issue No: Vol. 9, No. 2 (2024)
       
  • Electrophoretic maneuvering of nonuniformly charged particles suspended in
           linear flows: Impact of the medium viscoelasticity

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      Authors: Rajnandan Borthakur; Uddipta Ghosh
      First page: 023302
      Abstract: Author(s): Rajnandan Borthakur and Uddipta Ghosh
      Electrophoresis often coexists with imposed background flows in many applications. When particles carry nonuniform surface charge, and the fluid itself is complex, the particles may follow fascinating trajectories, as shown in this work. Indeed, the combined action of a background flow and complex fluidic medium may cause particles to undergo cross-stream migration. However, the very nature of its trajectory and the extent of its migration depends on whether the imposed flow or the electrophoretic propulsion dominates the motion. The insights provided here may be exploited for improving electrophoretic separation and sorting of particles based on their size and surface charge.
      [Phys. Rev. Fluids 9, 023302] Published Tue Feb 13, 2024
      Keywords: Complex and Non-Newtonian Fluids
      Citation: Phys. Rev. Fluids 9, 023302 (2024)
      PubDate: 2024-02-13T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023302
      Issue No: Vol. 9, No. 2 (2024)
       
  • Flow of a shear-thinning fluid in a rectangular duct

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      Authors: Ilya Barmak; Davide Picchi, Alexander Gelfgat, Neima Brauner
      First page: 023303
      Abstract: Author(s): Ilya Barmak, Davide Picchi, Alexander Gelfgat, and Neima Brauner
      A rigorous numerical solution for steady laminar flows of shear-thinning fluids in rectangular ducts is presented for the first time. We derive universal scaling laws for the effective viscosity that depends on the dimensionless rheological parameters and the effective channel size that is a function of the aspect ratio of the duct. These allow us to generalize the classical formula for the friction factor of Newtonian flows (12/Re) to Carreau fluids flowing in rectangular ducts of any aspect ratio, where the Reynolds number is based on the effective channel size and the effective viscosity.
      [Phys. Rev. Fluids 9, 023303] Published Tue Feb 13, 2024
      Keywords: Complex and Non-Newtonian Fluids
      Citation: Phys. Rev. Fluids 9, 023303 (2024)
      PubDate: 2024-02-13T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023303
      Issue No: Vol. 9, No. 2 (2024)
       
  • Thermal boundary layers in turbulent Rayleigh-Bénard convection with
           rough and smooth plates: A one-to-one comparison

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      Authors: Ronald du Puits
      First page: 023501
      Abstract: Author(s): Ronald du Puits
      Roughness at a surface hotter or colder than its environment may significantly enhance the convective heat transfer coefficient. This enhancement results from modification of the near-wall flow field. Our work demonstrates how roughness elements deform the temperature field compared to a smooth surface, and, under which conditions the heat transfer coefficient is enhanced.
      [Phys. Rev. Fluids 9, 023501] Published Tue Feb 13, 2024
      Keywords: Convection
      Citation: Phys. Rev. Fluids 9, 023501 (2024)
      PubDate: 2024-02-13T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023501
      Issue No: Vol. 9, No. 2 (2024)
       
  • Bolgiano-Obukhov scaling in two-dimensional Rayleigh-Bénard convection at
           extreme Rayleigh numbers

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      Authors: Roshan Samuel; Mahendra K. Verma
      First page: 023502
      Abstract: Author(s): Roshan Samuel and Mahendra K. Verma
      Through high-resolution direct numerical simulations, we demonstrate that energy transfers in two-dimensional (2D) thermal convection exhibit Bolgiano-Obukhov scaling. This is in contrast with convection in three dimensions which follows the Kolmogorov-Obukhov phenomenology. This difference arises from the presence of inverse cascade in 2D which leads to a negative kinetic energy flux at small wavenumbers. The magnitude of this flux decreases with wavenumber due to the effect of buoyancy. We also demonstrate that entropy dissipation in the thermal boundary layers displays a scaling law that is observable from the entropy flux curves.
      [Phys. Rev. Fluids 9, 023502] Published Fri Feb 16, 2024
      Keywords: Convection
      Citation: Phys. Rev. Fluids 9, 023502 (2024)
      PubDate: 2024-02-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023502
      Issue No: Vol. 9, No. 2 (2024)
       
  • Flow mode and global transport of liquid metal thermal convection in a
           cavity with $\mathrm{Γ}=1/3$

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      Authors: Xin-Yuan Chen (陈新元); Juan-Cheng Yang (阳倦成), Ming-Jiu Ni (倪明玖)
      First page: 023503
      Abstract: Author(s): Xin-Yuan Chen (陈新元), Juan-Cheng Yang (阳倦成), and Ming-Jiu Ni (倪明玖)
      In this experimental investigation we examine the dynamics of liquid metal thermal convection within an elongated cuboid cell with aspect ratio 1/3. We highlight the evolution of flow modes, transitioning from single- to double-roll mode, and transitional modes which are reconstructed by visualizing temperature data on the sidewall. As the Rayleigh number surpasses the critical value, the flow state transforms from a multiple-mode coexistence state to a single-roll mode-dominated configuration. Flow modes and global transport properties offer profound insights into the fundamental characteristics of thermal convection in liquid metals under strong lateral geometric confinement.
      [Phys. Rev. Fluids 9, 023503] Published Tue Feb 20, 2024
      Keywords: Convection
      Citation: Phys. Rev. Fluids 9, 023503 (2024)
      PubDate: 2024-02-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023503
      Issue No: Vol. 9, No. 2 (2024)
       
  • Reversal of the transverse force on a spherical bubble rising close to a
           vertical wall at moderate-to-high Reynolds numbers

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      Authors: Pengyu Shi
      First page: 023601
      Abstract: Author(s): Pengyu Shi
      Bubbles rising near a vertical wall are known to bounce repeatedly when the Reynolds number (Re) exceeds about 65. This behavior contradicts potential flow theory, which suggests a consistently attractive transverse force. In this study, we demonstrate through numerical simulations that below a critical Re-dependent separation, the transverse force decreases with decreasing separation, potentially reversing from attractive to repulsive. We believe this reversal is responsible for the bouncing motion observed in freely near-wall rising bubbles.
      [Phys. Rev. Fluids 9, 023601] Published Tue Feb 06, 2024
      Keywords: Drops, Bubbles, Capsules, and Vesicles
      Citation: Phys. Rev. Fluids 9, 023601 (2024)
      PubDate: 2024-02-06T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023601
      Issue No: Vol. 9, No. 2 (2024)
       
  • Shear-triggered coalescence

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      Authors: Alireza Mashayekhi; Coralie Vazquez, Hongying Zhao, Michael Gattrell, James F. Gilchrist, John M. Frostad
      First page: 023602
      Abstract: Author(s): Alireza Mashayekhi, Coralie Vazquez, Hongying Zhao, Michael Gattrell, James F. Gilchrist, and John M. Frostad
      In prior work, it was observed that some bitumen droplets coalesced faster when colliding in shear than colliding head-on. Inspired by this observation, we aimed to reproduce the same behavior in a simpler system composed of pure oil, water, and surfactants/particles. Using a cantilevered-capillary force apparatus we observed this phenomenon for droplets stabilized by cellulose nanocrystals and coined the term “shear-triggered coalescence” to describe it.
      [Phys. Rev. Fluids 9, 023602] Published Thu Feb 08, 2024
      Keywords: Drops, Bubbles, Capsules, and Vesicles
      Citation: Phys. Rev. Fluids 9, 023602 (2024)
      PubDate: 2024-02-08T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.023602
      Issue No: Vol. 9, No. 2 (2024)
       
  • Electrowetting dynamics of sessile droplets in a viscous medium

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      Authors: Juan S. Marin Quintero; Butunath Majhy, Prashant R. Waghmare
      First page: 024001
      Abstract: Author(s): Juan S. Marin Quintero, Butunath Majhy, and Prashant R. Waghmare
      This work analyzes the transient wetting dynamics of droplets in viscous media with appropriate governing parameters and examines the drop’s transient response immediately after the actuation, the drop’s retraction and resultant dynamics, and the effect of multiple wave actuation on the droplet transition.
      [Phys. Rev. Fluids 9, 024001] Published Wed Feb 07, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, 024001 (2024)
      PubDate: 2024-02-07T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024001
      Issue No: Vol. 9, No. 2 (2024)
       
  • Stability of traveling waves of a thermoviscous liquid film down the
           outer surface of a cylinder

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      Authors: Garima Singh; Naveen Tiwari
      First page: 024002
      Abstract: Author(s): Garima Singh and Naveen Tiwari
      The stability of a traveling wave on the outside of a heated solid vertical cylinder is considered. The axisymmetric traveling wave becomes unstable and leads to the formation of asymmetric droplets over the cylinder. Eigenvalue analysis indicates that at smaller wavenumbers, the gravity mode exists, and a thermocapillary mode also exists but at larger wavenumbers. Patterns generated using nonlinear analysis show that the selected mode is governed by the geometric confinement in the azimuthal direction. Interesting nonlinear patterns are obtained due to an interesting interplay between the gravity mode and thermocapillary mode.
      [Phys. Rev. Fluids 9, 024002] Published Tue Feb 13, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, 024002 (2024)
      PubDate: 2024-02-13T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024002
      Issue No: Vol. 9, No. 2 (2024)
       
  • Arresting of interfacial phase separation with an imposed flow

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      Authors: Ryuta X. Suzuki; Shoji Seya, Takahiko Ban, Manoranjan Mishra, Yuichiro Nagatsu
      First page: 024003
      Abstract: Author(s): Ryuta X. Suzuki, Shoji Seya, Takahiko Ban, Manoranjan Mishra, and Yuichiro Nagatsu
      We experimentally investigate displacement of a more viscous liquid by a less viscous one in a Hele-Shaw cell using an aqueous two phase system, where phase separation occurs in the growing liquid-liquid interfacial region, by varying the injection flow rate and the phase separation rate. We show that the degree of the interfacial phase separation scales as a unique function of the ratio of the flow and phase separation rates and it decreases with the ratio. These results demonstrate that the interfacial phase separation is arrested by the imposed flow and determined by competition between the flow and phase separation rates. The arresting effect and the mechanism are numerically verified.
      [Phys. Rev. Fluids 9, 024003] Published Wed Feb 14, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, 024003 (2024)
      PubDate: 2024-02-14T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024003
      Issue No: Vol. 9, No. 2 (2024)
       
  • Instability and rupture of sheared viscous liquid nanofilms

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      Authors: Vira Dhaliwal; Christian Pedersen, Kheireddin Kadri, Guillaume Miquelard-Garnier, Cyrille Sollogoub, Jorge Peixinho, Thomas Salez, Andreas Carlson
      First page: 024201
      Abstract: Author(s): Vira Dhaliwal, Christian Pedersen, Kheireddin Kadri, Guillaume Miquelard-Garnier, Cyrille Sollogoub, Jorge Peixinho, Thomas Salez, and Andreas Carlson
      Liquid nanofilms are subject to rupture due to intermolecular forces triggered by surface perturbations arising from thermal fluctuations. When a shear stress is imposed at the free surface it becomes stable in the direction of shear, but perturbations can still grow in the perpendicular direction to the shear.
      [Phys. Rev. Fluids 9, 024201] Published Thu Feb 08, 2024
      Keywords: Micro- and Nanofluidics
      Citation: Phys. Rev. Fluids 9, 024201 (2024)
      PubDate: 2024-02-08T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024201
      Issue No: Vol. 9, No. 2 (2024)
       
  • Prediction of the reaction yield in a X-micromixer given the mixing degree
           and the kinetic constant

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      Authors: S. Tomasi Masoni; A. Mariotti, M. Antognoli, C. Galletti, R. Mauri, M. V. Salvetti, E. Brunazzi
      First page: 024202
      Abstract: Author(s): S. Tomasi Masoni, A. Mariotti, M. Antognoli, C. Galletti, R. Mauri, M. V. Salvetti, and E. Brunazzi
      Understanding flow regimes and mixing in microreactors is crucial for achieving high reaction yields. This study combines simulations and experiments in an X-microreactor up to Reynolds number (Re) 600. For Re> 375, an unsteady periodic regime is observed with a collapsing central vortical structure and symmetric vorticity shedding. Counterrotating vortices form, merge, and recreate the central vortex. Despite increased mixing in this regime, reaction yield remains similar due to reduced reactant residence time. A model predicting reaction yield based on mixing degree and nominal kinetic constant is developed, successfully encompassing all flow regimes and Damköhler numbers (0.1 < Da < 103).
      [Phys. Rev. Fluids 9, 024202] Published Thu Feb 15, 2024
      Keywords: Micro- and Nanofluidics
      Citation: Phys. Rev. Fluids 9, 024202 (2024)
      PubDate: 2024-02-15T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024202
      Issue No: Vol. 9, No. 2 (2024)
       
  • Mathematical modeling of erosion and deposition in porous media

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      Authors: Hamad El Kahza; Pejman Sanaei
      First page: 024301
      Abstract: Author(s): Hamad El Kahza and Pejman Sanaei
      Using the Stokes equation for fluid flow and the advection-diffusion equation for the transport of solids, alongside threshold laws governing erosion and deposition, we present a model aimed at conducting a comprehensive analysis of both erosion and deposition processes within a porous medium composed of axisymmetric channels.
      [Phys. Rev. Fluids 9, 024301] Published Fri Feb 16, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 024301 (2024)
      PubDate: 2024-02-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024301
      Issue No: Vol. 9, No. 2 (2024)
       
  • Caustic formation in a non-Gaussian model for turbulent aerosols

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      Authors: J. Meibohm; L. Sundberg, B. Mehlig, K. Gustavsson
      First page: 024302
      Abstract: Author(s): J. Meibohm, L. Sundberg, B. Mehlig, and K. Gustavsson
      Caustic singularities of the spatial distribution of particles in turbulent aerosols enhance collision rates and accelerate coagulation. The rate of caustic formation depends sensitively on the particle inertia. We study caustic formation in a non-Gaussian statistical model to understand why there is a significant difference in formation rates between direct numerical simulations and Gaussian models. In the limit of small inertia, caustics form due to an optimal fluctuation of the Lagrangian fluid-velocity gradients, and we show that the formation rate depends sensitively on the tails of the gradient distribution, explaining the observed mismatch
      [Phys. Rev. Fluids 9, 024302] Published Fri Feb 16, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 024302 (2024)
      PubDate: 2024-02-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024302
      Issue No: Vol. 9, No. 2 (2024)
       
  • Role of flow structures on the deposition of low-inertia particles in
           turbulent pipe flow

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      Authors: Rasmus Korslund Schlander; Stelios Rigopoulos, George Papadakis
      First page: 024303
      Abstract: Author(s): Rasmus Korslund Schlander, Stelios Rigopoulos, and George Papadakis
      We characterize the role of coherent structures on the transport and wall deposition of low-inertia particles in a turbulent pipe flow using extended proper orthogonal decomposition (EPOD) and spectral analysis. The equilibrium Eulerian approach is employed to model particle velocity and concentration. A new Fukagata-Iwamoto-Kasagi (FIK) identity is derived for the wall deposition rate coefficient (Sherwood number) and employed to quantify the contributions of the mean and fluctuating velocity and particle concentration fields for different Stokes, Froude and Reynolds numbers. New terms appear due to the inertia of the particles that encapsulate the turbophoresis effect.
      [Phys. Rev. Fluids 9, 024303] Published Tue Feb 20, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 024303 (2024)
      PubDate: 2024-02-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024303
      Issue No: Vol. 9, No. 2 (2024)
       
  • From discrete to continuum description of weakly inertial bedload
           transport

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      Authors: Benjamin Fry; Laurent Lacaze, Thomas Bonometti, Pierre Elyakime, François Charru
      First page: 024304
      Abstract: Author(s): Benjamin Fry, Laurent Lacaze, Thomas Bonometti, Pierre Elyakime, and François Charru
      Granular bedload plays a crucial role in shaping streams and influencing their development over time. This process involves the movement of grains along the stream bed surface driven by the shear stress from the flowing water. For an accurate model on a practical scale, it is essential to grasp the key properties of the granular layer interacting with the water. Our focus lies in understanding the rheological characteristics of the water grain mixture when grain movement is localized within a thin layer near the bed surface and under a weakly inertial regime. This aims to expand our understanding of viscous-laminar properties mostly described for a thick shear layer in the literature.
      [Phys. Rev. Fluids 9, 024304] Published Tue Feb 20, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 024304 (2024)
      PubDate: 2024-02-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024304
      Issue No: Vol. 9, No. 2 (2024)
       
  • Shear-induced particle migration in viscous suspensions with continuous
           size distribution

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      Authors: O. M. Lavrenteva; I. Smagin, A. Nir
      First page: 024305
      Abstract: Author(s): O. M. Lavrenteva, I. Smagin, and A. Nir
      A novel approach to study of the shear-induced diffusion of particles in suspensions with continuous particle size distribution is suggested. It addresses the migration of local moments of the size distribution. Particle size distribution at each point is consequently obtained from the resulting moments, by solving inverse problems locally. For a particular example of stationary flow in a circular tube, we present results that include concentration inhomogeneity, moments’ distributions and the consequent local continuous particle size distributions. The similarity and difference from cases of monodispersed suspensions are discussed.
      [Phys. Rev. Fluids 9, 024305] Published Tue Feb 20, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 024305 (2024)
      PubDate: 2024-02-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024305
      Issue No: Vol. 9, No. 2 (2024)
       
  • Data-assisted, physics-informed propagators for recurrent flows

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      Authors: T. Lichtenegger
      First page: 024401
      Abstract: Author(s): T. Lichtenegger
      Computational fluid dynamics simulations of dynamic flows usually entail large numerical costs. Over the last few years, several data-driven methods, partly of significant complexity, have been devised to mitigate CPU times while still capturing the relevant physics. In this work, a very simple approach with a clear physical interpretation is presented that splits the problem into a linear and a nonlinear part. Based on a database of precomputed reference states, predictions are made using the method of analogues (nonlinear dynamics) together with physics-informed propagators that capture and correct for any deviation from the nearest reference state in a linear fashion.
      [Phys. Rev. Fluids 9, 024401] Published Tue Feb 20, 2024
      Keywords: Nonlinear Dynamical Systems
      Citation: Phys. Rev. Fluids 9, 024401 (2024)
      PubDate: 2024-02-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024401
      Issue No: Vol. 9, No. 2 (2024)
       
  • Turbulent puffs in transitional pulsatile pipe flow at moderate pulsation
           amplitudes

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      Authors: Daniel Morón; Marc Avila
      First page: 024601
      Abstract: Author(s): Daniel Morón and Marc Avila
      Pulsatile pipe flow, or the flow in a pipe with a mean and one or more harmonic bulk velocity components, is a benchmark to study unsteady driven flows in industrial and biological applications. We study the transitional regime of pulsatile pipe flow at moderate-to-high amplitudes and intermediate pulsation frequencies. We show that, as in steady driven pipe flow, the first long-lived turbulent structures are localized. We combine direct numerical simulations, causal analysis and turbulence modeling to describe the behavior of these turbulent patches in pulsatile pipe flow, and to determine the physical mechanisms by which they survive the pulsation.
      [Phys. Rev. Fluids 9, 024601] Published Thu Feb 08, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 024601 (2024)
      PubDate: 2024-02-08T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024601
      Issue No: Vol. 9, No. 2 (2024)
       
  • Turbulent power theory in heavy-ion plasma of a Jovian magnetosphere

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      Authors: Vitaliy Kaminker
      First page: 024602
      Abstract: Author(s): Vitaliy Kaminker
      Turbulent power is introduced in to Jupiter’s magnetosphere near the cen- trifugal equator of the plasma disc. Turbulent fluctuations are generated within the plasma fluid. Turbulent energy then travels out of the plasma disc via shear Alfvén waves, dissipating out of the system along the way.
      [Phys. Rev. Fluids 9, 024602] Published Tue Feb 13, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 024602 (2024)
      PubDate: 2024-02-13T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024602
      Issue No: Vol. 9, No. 2 (2024)
       
  • Predicting unavailable parameters from existing velocity fields of
           turbulent flows using a GAN-based model

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      Authors: Linqi Yu; Mustafa Z. Yousif, Young-Woo Lee, Xiaojue Zhu, Meng Zhang, Paraskovia Kolesova, Hee-Chang Lim
      First page: 024603
      Abstract: Author(s): Linqi Yu, Mustafa Z. Yousif, Young-Woo Lee, Xiaojue Zhu, Meng Zhang, Paraskovia Kolesova, and Hee-Chang Lim
      This study developed a mapping generative adversarial network (M-GAN) to predict unavailable parameters: streamwise velocity, temperature, and pressure from available velocity components. Two-dimensional Rayleigh–Bénard flow and turbulent channel flow are used to evaluate M-GAN performance. The results indicate that the proposed model has good capability to map the available parameters to unavailable parameters. Furthermore, M-GAN also has good generalization to predict the parameters from channel flows at different Reynolds numbers.
      [Phys. Rev. Fluids 9, 024603] Published Tue Feb 20, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 024603 (2024)
      PubDate: 2024-02-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024603
      Issue No: Vol. 9, No. 2 (2024)
       
  • Internal gravity waves in stratified flows with and without vortical modes

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      Authors: Vincent Labarre; Pierre Augier, Giorgio Krstulovic, Sergey Nazarenko
      First page: 024604
      Abstract: Author(s): Vincent Labarre, Pierre Augier, Giorgio Krstulovic, and Sergey Nazarenko
      We analyze direct numerical simulations of stratified turbulence without shear modes, and with or without vortical modes at various Froude and buoyancy Reynolds numbers. It allows us to investigate the effects of vortical modes on the dynamics of stratified flows. A spatiotemporal analysis reveals slow internal gravity waves interacting by triadic resonance instabilities in our strongly stratified flow simulations such as the one in the figure. We observe that removing vortical modes helps to concentrate the energy around the wave frequency, but it is not enough to observe a weak internal gravity wave’s turbulence regime.
      [Phys. Rev. Fluids 9, 024604] Published Tue Feb 20, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 024604 (2024)
      PubDate: 2024-02-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.024604
      Issue No: Vol. 9, No. 2 (2024)
       
  • Autothermotaxis of volatile drops

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      Authors: Pallav Kant; Mathieu Souzy, Nayoung Kim, Devaraj van der Meer, Detlef Lohse
      First page: L012001
      Abstract: Author(s): Pallav Kant, Mathieu Souzy, Nayoung Kim, Devaraj van der Meer, and Detlef Lohse
      We present an extraordinary phenomenon that emerges from seemingly simple ingredients: a volatile droplet deposited on a highly wetting and heat-conducting warm substrate. Contrary to prevailing intuition that the deposited droplet would spread more and evaporate faster, we find that the droplet instead undergoes contraction and in addition it spontaneously and erratically moves, for substrate temperatures well below the boiling point of the liquid. We term this remarkable phenomenon “Autothermotaxis” and show that it originates from the thermal Marangoni flow in the droplet which undergoes an instability. The thermal Marangoni flow is also the reason for the contraction of the droplet.
      [Phys. Rev. Fluids 9, L012001] Published Wed Jan 31, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, L012001 (2024)
      PubDate: 2024-01-31T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.L012001
      Issue No: Vol. 9, No. 1 (2024)
       
  • Unifying length-scale-based rheology of dense suspensions

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      Authors: Zhuan Ge; Teng Man, Herbert E. Huppert, Kimberly M. Hill, Sergio Andres Galindo-Torres
      First page: L012302
      Abstract: Author(s): Zhuan Ge, Teng Man, Herbert E. Huppert, Kimberly M. Hill, and Sergio Andres Galindo-Torres
      Suspensions, comprising particles and fluid, play a crucial role across diverse domains, including in nature, such as submarine landslides, biological systems such as blood flows, as well as industrial materials like concrete. The rheology of these materials is a combination of both fluid and solid properties. This study introduces a dimensionless number derived from the ratio between characteristic length scales, offering a unified perspective on the rheology of dense suspensions across a spectrum from conditions where fluid-like effects dominate to regimes influenced by inertial forces. The derivation contained herein is strict, offering significant physical insight into these systems.
      [Phys. Rev. Fluids 9, L012302] Published Tue Jan 30, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, L012302 (2024)
      PubDate: 2024-01-30T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.L012302
      Issue No: Vol. 9, No. 1 (2024)
       
  • Simple generalization of kinetic theory for granular flows of
           nonspherical, oriented particles

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      Authors: Dalila Vescovi; Ben Nadler, Diego Berzi
      First page: L012301
      Abstract: Author(s): Dalila Vescovi, Ben Nadler, and Diego Berzi
      The collective motion of nonspherical particles displaying preferential alignment can be modeled by extending the kinetic theory of granular gases. A linear dependency on the orientational tensor into the constitutive relations for the stresses, and a balance law for the orientational tensor itself, in which a key role is played by the randomizing effect of collisions, permit to reproduce the discrete simulations of homogeneous shearing flows of cylinders at different aspect ratios.
      [Phys. Rev. Fluids 9, L012301] Published Tue Jan 16, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, L012301 (2024)
      PubDate: 2024-01-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.L012301
      Issue No: Vol. 9, No. 1 (2024)
       
  • Forced and natural dynamics of a clamped flexible fiber in wall turbulence

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      Authors: Giulio Foggi Rota; Morie Koseki, Riya Agrawal, Stefano Olivieri, Marco Edoardo Rosti
      First page: L012601
      Abstract: Author(s): Giulio Foggi Rota, Morie Koseki, Riya Agrawal, Stefano Olivieri, and Marco Edoardo Rosti
      In turbulent flows, slender flexible bodies exhibit complex motions such as the swaying of seagrass or the oscillations of a pylon in the wind. Here we characterize the dynamical behavior of a clamped flexible fiber immersed in wall turbulence over a wide range of natural frequencies by DNS. Only two flapping states are possible: one where the fiber oscillates at the characteristic frequency of the largest turbulent eddies and another where the natural structural response dominates. We observe for the first time that in the turbulence dominated regime the fiber always sways at a frequency proportional to the largest scale of the flow, regardless of its structural parameters.
      [Phys. Rev. Fluids 9, L012601] Published Fri Jan 12, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, L012601 (2024)
      PubDate: 2024-01-12T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.L012601
      Issue No: Vol. 9, No. 1 (2024)
       
  • Marangoni vortex rings in miscible spreading

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      Authors: Anurag Pant; Baburaj. A Puthenveettil
      First page: L012701
      Abstract: Author(s): Anurag Pant and Baburaj. A Puthenveettil
      This work investigates the dynamics of a unique, radially expanding vortex ring in a water layer when a miscible, volatile drop of ethanol spreads as a film on the air-water interface. The study unravels the link between the dynamics at the interface and the generation of vorticity in the water layer below it. A novel scaling is proposed for the radius and velocity of such vortex rings, where they are shown to be dependent on time as well as the properties of the drop and the substrate.
      [Phys. Rev. Fluids 9, L012701] Published Thu Jan 11, 2024
      Keywords: Vortex Dynamics
      Citation: Phys. Rev. Fluids 9, L012701 (2024)
      PubDate: 2024-01-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.L012701
      Issue No: Vol. 9, No. 1 (2024)
       
  • Editorial: The 2023 François Naftali Frenkiel Award for Fluid
           Mechanics

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      Authors: Eric Lauga; Beverley McKeon
      First page: 010001
      Abstract: Author(s): Eric Lauga and Beverley McKeon
      [Phys. Rev. Fluids 9, 010001] Published Wed Jan 31, 2024
      Keywords: Editorials and Announcements
      Citation: Phys. Rev. Fluids 9, 010001 (2024)
      PubDate: 2024-01-31T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.010001
      Issue No: Vol. 9, No. 1 (2024)
       
  • Air-cushioning below an impacting wave-structured disk: Free-surface
           deformation and slamming load

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      Authors: Yee Li (Ellis) Fan; Utkarsh Jain, Devaraj van der Meer
      First page: 010501
      Abstract: Author(s): Yee Li (Ellis) Fan, Utkarsh Jain, and Devaraj van der Meer
      A radially symmetric sinusoidal wave structure is imprinted on an impacting circular disk to modulate the way the disk forces the free water surface. The experiments support the argument that the surface elevation around the disk edge prior to impact is an instability of the Kelvin-Helmholtz type, as the free surface resonates when the forcing wavelength on the disk is close to the most unstable wavelength predicted by theory. Besides, our wave-structured disk is also found to promote gradual inertial wetting of the impacting surface to effectively retain the entrapped air pocket (as shown in the figure), which, in turn, mitigates the peak impact force.
      [Phys. Rev. Fluids 9, 010501] Published Wed Jan 10, 2024
      Keywords: Invited Articles
      Citation: Phys. Rev. Fluids 9, 010501 (2024)
      PubDate: 2024-01-10T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.010501
      Issue No: Vol. 9, No. 1 (2024)
       
  • Electro-poroelastohydrodynamics of the endothelial glycocalyx layer and
           streaming potential in wavy-wall microvessels

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      Authors: C. Teodoro; J. Arcos, O. Bautista, F. Méndez
      First page: 013101
      Abstract: Author(s): C. Teodoro, J. Arcos, O. Bautista, and F. Méndez
      The study of the endothelial glycocalyx layer (EGL) has been of great interest in recent years due to its direct relationship with human health. Some works have modeled the EGL under the triphasic mixture theory (TMT), considering an electrically charged porous medium interacting with the electrolyte under a pressure gradient. Our study is based on a model that couples the mechanical and electrical interaction, considering TMT, a non-Newtonian electrolyte, and wavy walls using the domain perturbation method, focusing on the shear stresses in the EGL and on the induced streaming potential that can be used as a biocompatible energy source.
      [Phys. Rev. Fluids 9, 013101] Published Tue Jan 16, 2024
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 9, 013101 (2024)
      PubDate: 2024-01-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013101
      Issue No: Vol. 9, No. 1 (2024)
       
  • Conformations, correlations, and instabilities of a flexible fiber in an
           active fluid

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      Authors: Scott Weady; David B. Stein, Alexandra Zidovska, Michael J. Shelley
      First page: 013102
      Abstract: Author(s): Scott Weady, David B. Stein, Alexandra Zidovska, and Michael J. Shelley
      Many biological systems rely on interactions between active processes and passive, deformable structures to properly function. An important example is chromatin in the cell nucleus, where ATP-powered processes, such as transcription or DNA repair, act on the chromatin fiber and influence its motion. Motivated by this system, in this study we develop and analyze a model of a flexible fiber in an active suspension as an analog to a chromatin fiber in an active environment - the nucleoplasm. Interactions between the suspension and the fiber lead to a novel bend instability, and nonlinear simulations identify coherent motions and conformations of the fiber over long timescales.
      [Phys. Rev. Fluids 9, 013102] Published Thu Jan 18, 2024
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 9, 013102 (2024)
      PubDate: 2024-01-18T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013102
      Issue No: Vol. 9, No. 1 (2024)
       
  • Activity-induced asymmetric dispersion in confined channels with
           constriction

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      Authors: Armin Maleki; Malihe Ghodrat, Ignacio Pagonabarraga
      First page: 013103
      Abstract: Author(s): Armin Maleki, Malihe Ghodrat, and Ignacio Pagonabarraga
      Our Brownian dynamics model uncovers response mechanisms of microorganisms such as Escherichia coli to shear flows and constrictions, shedding light on anomalous accumulation of active particles in confined channels. Our findings highlight the butterfly-like attractors that trap particles past the constriction and characterize relevant dynamical regimes of active particle accumulation. We also explore the impact of particle size, channel geometry, and fluid velocity on trapping probability and accumulation strength. This intriguing phenomenon could be utilized as geometrical sift for mixture of active particles with different sizes/velocities and lead to innovations in particle manipulation.
      [Phys. Rev. Fluids 9, 013103] Published Thu Jan 18, 2024
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 9, 013103 (2024)
      PubDate: 2024-01-18T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013103
      Issue No: Vol. 9, No. 1 (2024)
       
  • Elastic instability in a family of rectilinear viscoelastic channel flows
           devoid of centerline symmetry

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      Authors: Shailendra Kumar Yadav; Ganesh Subramanian, V. Shankar
      First page: 013301
      Abstract: Author(s): Shailendra Kumar Yadav, Ganesh Subramanian, and V. Shankar
      The recently discovered elastic center-mode instability in plane-Poiseuille flow is shown to be present even in base flows devoid of centerline symmetry. This is illustrated using the Couette-Poiseuille family of asymmetric velocity profiles, wherein the instability is present when the maximum of the base flow is present within the channel domain. The predicted instability is potentially relevant to viscoelastic flows in the Taylor-Dean, shallow-cavity, and slider-bearing configurations.
      [Phys. Rev. Fluids 9, 013301] Published Mon Jan 29, 2024
      Keywords: Complex and Non-Newtonian Fluids
      Citation: Phys. Rev. Fluids 9, 013301 (2024)
      PubDate: 2024-01-29T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013301
      Issue No: Vol. 9, No. 1 (2024)
       
  • Molecular diffusion of mass and energy predicted by ab initio potential
           energy surfaces for air components at high temperatures

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      Authors: Paolo Valentini; Maninder S. Grover, Nicholas J. Bisek
      First page: 013401
      Abstract: Author(s): Paolo Valentini, Maninder S. Grover, and Nicholas J. Bisek
      The accurate characterization of molecular transport properties is essential for high-fidelity simulations of reactive, hypersonic flows. The correct prediction of energy and mass diffusion in the laminar, high-temperature, multicomponent boundary layer of a hyper-velocity flow has profound implications for the accurate modeling of gas-surface interactions and thermal loads on the aeroshell. In this work, molecular transport is investigated by solely using ab initio potential energy surfaces. Our approach removes the empiricism associated with simplified molecular interactions models used in previous studies and is applicable to arbitrary gas mixtures.
      [Phys. Rev. Fluids 9, 013401] Published Tue Jan 09, 2024
      Keywords: Compressible and Rarefied Flows, Kinetic Theory
      Citation: Phys. Rev. Fluids 9, 013401 (2024)
      PubDate: 2024-01-09T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013401
      Issue No: Vol. 9, No. 1 (2024)
       
  • Pulsation mechanism of a Taylor cone under a single pulse voltage

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      Authors: Jin-bo Cheng; Qi-you Liu, Li-jun Yang, Jun-xue Ren, Hai-bin Tang, Qing-fei Fu, Luo Xie
      First page: 013701
      Abstract: Author(s): Jin-bo Cheng, Qi-you Liu, Li-jun Yang, Jun-xue Ren, Hai-bin Tang, Qing-fei Fu, and Luo Xie
      Using a needle-plate electro-atomization experimental device, and applying a single pulse disturbance voltage signal, the response of the Taylor cone to a disturbance signal was explored. At the experimental level, the coupling relationship between polarization charge relaxation time and the oscillation period of the Taylor cone was uncovered, revealing the oscillation mechanism of the Taylor cone under this voltage disturbance.
      [Phys. Rev. Fluids 9, 013701] Published Mon Jan 08, 2024
      Keywords: Electrokinetic Phenomena, Electrohydrodynamics, and Magnetohydrodynamics
      Citation: Phys. Rev. Fluids 9, 013701 (2024)
      PubDate: 2024-01-08T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013701
      Issue No: Vol. 9, No. 1 (2024)
       
  • Adjoint-based machine learning for active flow control

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      Authors: Xuemin Liu; Jonathan F. MacArt
      First page: 013901
      Abstract: Author(s): Xuemin Liu and Jonathan F. MacArt
      We develop neural-network active flow controllers through a deep learning PDE augmentation method (DPM). In two-dimensional, incompressible, confined cylinder flow with Re = 100, we compare drag-reduction performance and optimization cost of adjoint-based controllers and deep reinforcement learning (DRL)-based controllers. The DRL-based controller demands 4,229 times the model complexity of the DPM-based one. The DPM-based controller is 4.85 times more effective and 63.2 times less computationally intensive to train than the DRL-based counterpart. In laminar compressible flows, successful extrapolation of the controller to out-of-sample flows demonstrates the robustness of the learning approach.
      [Phys. Rev. Fluids 9, 013901] Published Tue Jan 09, 2024
      Keywords: Instability, Transition, and Control
      Citation: Phys. Rev. Fluids 9, 013901 (2024)
      PubDate: 2024-01-09T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013901
      Issue No: Vol. 9, No. 1 (2024)
       
  • Onset of Rayleigh-Bénard convection in dielectric liquids with
           electric conduction

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      Authors: Yuxing Peng; R. Deepak Selvakumar, Jian Wu
      First page: 013902
      Abstract: Author(s): Yuxing Peng, R. Deepak Selvakumar, and Jian Wu
      The convective flow of dielectric liquids with finite electric conductivity subjected to the simultaneous action of an electric field and a destabilizing temperature gradient is investigated. The instability of the system is studied through modal stability analysis, and it is found that the onset of the flow is delayed when an electric field is applied. Numerical simulations are performed to show the flow patterns and heat transfer characteristics. The dual solutions are highlighted in the bifurcation diagram.
      [Phys. Rev. Fluids 9, 013902] Published Tue Jan 16, 2024
      Keywords: Instability, Transition, and Control
      Citation: Phys. Rev. Fluids 9, 013902 (2024)
      PubDate: 2024-01-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013902
      Issue No: Vol. 9, No. 1 (2024)
       
  • Absolute and convective instability of a round jet emerging into an
           ambient medium of different viscosity

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      Authors: Jinwei Yang; Vinod Srinivasan
      First page: 013903
      Abstract: Author(s): Jinwei Yang and Vinod Srinivasan
      The case of a round jet of one liquid emerging into an ambient medium of a different viscosity is relevant to many industrial mixing situations. A linear spatiotemporal analysis of such a configuration shows that for sufficiently high viscosity contrast, the flow is absolutely unstable. Both axisymmetric and helical modes are unstable, with the axisymmetric mode being slightly dominant. The absolute/convective instability transition boundary defined in terms of viscosity ratio and jet Reynolds number is compared to the results of recent experiments and good agreement is found.
      [Phys. Rev. Fluids 9, 013903] Published Wed Jan 17, 2024
      Keywords: Instability, Transition, and Control
      Citation: Phys. Rev. Fluids 9, 013903 (2024)
      PubDate: 2024-01-17T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013903
      Issue No: Vol. 9, No. 1 (2024)
       
  • Modal and nonmodal stability analysis of turbulent stratified channel
           flows

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      Authors: Donato Variale; Enza Parente, Jean Christophe Robinet, Stefania Cherubini
      First page: 013904
      Abstract: Author(s): Donato Variale, Enza Parente, Jean Christophe Robinet, and Stefania Cherubini
      This work aims at studying the modal and nonmodal stability of stably stratified turbulent channel flow, assessing the influence of stratification at fixed friction Reynolds number. When increasing the stratification, the energy gain for streamwise-independent perturbations increases by two orders of magnitude, and the spanwise wavenumber for which the energy gain peaks reaches values comparable to those reported in the direct numerical simulations. Moreover, for nonzero values of the streamwise and spanwise wavenumbers, α and β, the energy gain curve has two peaks, one for shorter target times and α>β, leading to a center-channel temperature peak, and another for α
      Keywords: Instability, Transition, and Control
      Citation: Phys. Rev. Fluids 9, 013904 (2024)
      PubDate: 2024-01-29T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.013904
      Issue No: Vol. 9, No. 1 (2024)
       
  • Self-diffusiophoresis with bulk reaction

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      Authors: Rodolfo Brandão; Gunnar G. Peng, David Saintillan, Ehud Yariv
      First page: 014001
      Abstract: Author(s): Rodolfo Brandão, Gunnar G. Peng, David Saintillan, and Ehud Yariv
      Catalytic motors, which self-propel in a liquid due to an inhomogeneous surface reaction, constitute an important illustration of active matter in a non-biological context. Prevailing models of the associated self-diffusiophoretic transport assume a chemical reaction at the boundary of the swimmer. We here address the more realistic scenario where that reaction is balanced by a homogeneous reaction in the bulk. The associated diffusive transport of solute, described by two Damköhler numbers, exhibits a boundary-layer topology which is not encountered in the prevailing models.
      [Phys. Rev. Fluids 9, 014001] Published Wed Jan 03, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, 014001 (2024)
      PubDate: 2024-01-03T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014001
      Issue No: Vol. 9, No. 1 (2024)
       
  • Front tracking simulation of droplet displacement on solid surfaces by
           soluble surfactant-driven flows

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      Authors: Xinglong Shang; Zhengyuan Luo, Bofeng Bai, Long He, Guoqing Hu
      First page: 014002
      Abstract: Author(s): Xinglong Shang, Zhengyuan Luo, Bofeng Bai, Long He, and Guoqing Hu
      Comprehensive numerical investigations of droplet displacement in soluble surfactant driven flows using the front-tracking method are presented. Surfactant transport in the bulk and at interfaces shapes droplet displacement and determines the transition conditions between steady-state sliding and detachment. Detachment is highly dependent on surfactant replenishment at interfaces, especially at receding contact lines where the nonuniform concentration induced Marangoni flow impedes movement. The critical effective capillary number can be used as a criterion to evaluate the ability of the surfactant to detach the droplet, giving a unique logarithmic relationship with detachment time.
      [Phys. Rev. Fluids 9, 014002] Published Tue Jan 09, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, 014002 (2024)
      PubDate: 2024-01-09T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014002
      Issue No: Vol. 9, No. 1 (2024)
       
  • Flow stability in shallow droplets subject to localized heating of the
           bottom plate

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      Authors: Khang Ee Pang; Charles Cuvillier, Yutaku Kita, Lennon Ó Náraigh
      First page: 014003
      Abstract: Author(s): Khang Ee Pang, Charles Cuvillier, Yutaku Kita, and Lennon Ó Náraigh
      When the surface tension of a droplet or a film varies inhomogeneously, a surface-tension gradient occurs, which induces a flow inside the fluid. Thermocapillary flows induced by localized heating have been observed experimentally in millimeter-sized water droplets. In particular, these experiments reveal that when such droplets are heated from below by a localized heat source targeted at the droplet center, a twin vortex pair perpendicular to the substrate is observed. This work aims to obtain some theoretical understanding to explain the onset of such vortices.
      [Phys. Rev. Fluids 9, 014003] Published Tue Jan 16, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, 014003 (2024)
      PubDate: 2024-01-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014003
      Issue No: Vol. 9, No. 1 (2024)
       
  • Linear stability of ultrathin spherical coatings

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      Authors: D. Moreno-Boza; A. Sevilla
      First page: 014004
      Abstract: Author(s): D. Moreno-Boza and A. Sevilla
      This work investigates the linear stability of an ultrathin non-wetting liquid film on a spherical substrate in the limit of negligible inertia. The interplay between destabilizing van der Waals forces, with an exact potential description, and stabilizing surface tension gives rise to a discrete set of unstable temporal modes. Also, the performance of classical lubrication models has been assessed against the complete Stokes equations of motion.
      [Phys. Rev. Fluids 9, 014004] Published Wed Jan 24, 2024
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 9, 014004 (2024)
      PubDate: 2024-01-24T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014004
      Issue No: Vol. 9, No. 1 (2024)
       
  • Spectral analysis for elastica dynamics in a shear flow

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      Authors: Lujia Liu; Paweł Sznajder, Maria L. Ekiel-Jeżewska
      First page: 014101
      Abstract: Author(s): Lujia Liu, Paweł Sznajder, and Maria L. Ekiel-Jeżewska
      Equations are derived for the evolution of a three-dimensional perturbation of a straight slender elastic fiber at an arbitrary orientation in shear flow at low-Reynolds-number. For the orientation in the plane of the shear flow and the flow gradient, the spectral analysis is performed for in-plane and out-of-plane perturbations. The most unstable eigenfunctions and eigenvalues are analyzed and compared to the previous results for the in-plane perturbations in the shear flow, and for arbitrary perturbations in the compressional flow.
      [Phys. Rev. Fluids 9, 014101] Published Tue Jan 16, 2024
      Keywords: Laminar and Viscous Flows
      Citation: Phys. Rev. Fluids 9, 014101 (2024)
      PubDate: 2024-01-16T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014101
      Issue No: Vol. 9, No. 1 (2024)
       
  • Hydrodynamic bound states of rotating microcylinders in a confining
           geometry

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      Authors: Hanliang Guo; Yi Man, Hai Zhu
      First page: 014102
      Abstract: Author(s): Hanliang Guo, Yi Man, and Hai Zhu
      Locomotion is a combination of translation and rotation. With suitable boundary conditions, rotation can induce translation. The induced translations are more intriguing when multiple objects are rotating together. In this paper, we study theoretically the hydrodynamic bound states of two active cylinders rotating inside cylindrical confinement filled with viscous fluid. We find that the active cylinder pair can fall into four distinct non-trivial hydrodynamic bound states depending on their initial positions. Our findings may be helpful in understanding bacterial flagella rotating within a confining geometry.
      [Phys. Rev. Fluids 9, 014102] Published Thu Jan 25, 2024
      Keywords: Laminar and Viscous Flows
      Citation: Phys. Rev. Fluids 9, 014102 (2024)
      PubDate: 2024-01-25T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014102
      Issue No: Vol. 9, No. 1 (2024)
       
  • Colloidal diffusiophoresis in crossed electrolyte gradients: Experimental
           demonstration of an “action-at-a-distance” effect predicted by the
           Nernst-Planck equations

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      Authors: Ian Williams; Patrick B. Warren, Richard P. Sear, Joseph L. Keddie
      First page: 014201
      Abstract: Author(s): Ian Williams, Patrick B. Warren, Richard P. Sear, and Joseph L. Keddie
      We have conducted experiments which show that when two sources of different salts dissolving in water overlap, colloidal particles suspended anywhere in the solution move due to an action-at-a-distance force. As soon as the salts from the pair of sources overlap, an electric field appears practically instantaneously throughout the solution. The electric field exerts a force on any charged colloidal particles, causing them to move at speeds of order 0.1 micrometer/s. This new way of moving particles suspended in water could be used, for example, to remove them from solution, thereby purifying the water.
      [Phys. Rev. Fluids 9, 014201] Published Thu Jan 04, 2024
      Keywords: Micro- and Nanofluidics
      Citation: Phys. Rev. Fluids 9, 014201 (2024)
      PubDate: 2024-01-04T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014201
      Issue No: Vol. 9, No. 1 (2024)
       
  • Self-organization of autophoretic suspensions in confined shear flows

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      Authors: Prathmesh Vinze; Sebastien Michelin
      First page: 014202
      Abstract: Author(s): Prathmesh Vinze and Sebastien Michelin
      Phoretic particles swim and interact exploiting their dual chemical and hydrodynamic footprint on their environment, resulting in complex collective behavior spontaneously but also in response to external forcing. Here, based on a kinetic model for dilute suspensions, we numerically characterize their response to shear in a confined environment and identify three different regimes depending on the relative magnitude of shear forcing, chemotaxis, self-propulsion and confinement. The particles, in turn, exert microscopic stresses on their surroundings, resulting in a complex rheological response tightly linked to the self-organization regime.
      [Phys. Rev. Fluids 9, 014202] Published Mon Jan 22, 2024
      Keywords: Micro- and Nanofluidics
      Citation: Phys. Rev. Fluids 9, 014202 (2024)
      PubDate: 2024-01-22T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014202
      Issue No: Vol. 9, No. 1 (2024)
       
  • Sound waves, diffusive transport, and wall slip in nanoconfined
           compressible fluids

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      Authors: Hannes Holey; Peter Gumbsch, Lars Pastewka
      First page: 014203
      Abstract: Author(s): Hannes Holey, Peter Gumbsch, and Lars Pastewka
      In this work we compare long wavelength fluctuations in nanoconfined simple fluids from molecular dynamics simulations with continuum descriptions. Quasi-two-dimensional descriptions of these confined fluids give rise to attenuation behavior of hydrodynamic fluctuations distinct from the bulk. Interactions with the walls introduce additional dissipation and can be related to wall slip and an anomalous dispersion relation for sound.
      [Phys. Rev. Fluids 9, 014203] Published Mon Jan 29, 2024
      Keywords: Micro- and Nanofluidics
      Citation: Phys. Rev. Fluids 9, 014203 (2024)
      PubDate: 2024-01-29T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014203
      Issue No: Vol. 9, No. 1 (2024)
       
  • Attraction of neutrally buoyant deformable particles towards a vortex

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      Authors: Yutaro Fujiki; Hideto Awai, Yutaro Motoori, Susumu Goto
      First page: 014301
      Abstract: Author(s): Yutaro Fujiki, Hideto Awai, Yutaro Motoori, and Susumu Goto
      Deformable elastic particles can accumulate around a vortex center even if the particle is neutrally buoyant. The angle between the deformed particle and the pathline plays important roles in this accumulation process. In this paper, we propose a simple model to explain this interesting accumulation phenomenon.
      [Phys. Rev. Fluids 9, 014301] Published Thu Jan 04, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 014301 (2024)
      PubDate: 2024-01-04T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014301
      Issue No: Vol. 9, No. 1 (2024)
       
  • Irregular dependence on Stokes number, and nonergodic transport, of heavy
           inertial particles in steady laminar flows

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      Authors: Anu V. S. Nath; Anubhab Roy, S. Ravichandran, Rama Govindarajan
      First page: 014302
      Abstract: Author(s): Anu V. S. Nath, Anubhab Roy, S. Ravichandran, and Rama Govindarajan
      The dispersion of heavy inertial particles in a cellular flow made of Taylor-Green vortices is found to display non-ergodicity and sensitive dependence on initial particle location. Even more surprising is the sensitive and non-monotonic dependence on Stokes number. The large time dispersion of particles can be ballistic (red), diffusive (green) or trapped (blue), depending on where they have started in the flow. Diffusive particles show chaotic dynamics. Here the mutually exclusive group of initial particle locations form a non-ergodic set (as in the figure), unlike a turbulent flow, which is known to be ergodic.
      [Phys. Rev. Fluids 9, 014302] Published Tue Jan 09, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 014302 (2024)
      PubDate: 2024-01-09T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014302
      Issue No: Vol. 9, No. 1 (2024)
       
  • Pore-corner networks unveiled: Extraction and interactions in porous media

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      Authors: Ninghua Zhan; Yiping Wang, Xiang Lu, Rui Wu, Abdolreza Kharaghani
      First page: 014303
      Abstract: Author(s): Ninghua Zhan, Yiping Wang, Xiang Lu, Rui Wu, and Abdolreza Kharaghani
      A novel pore-corner network extraction method is proposed. To validate our proposed extraction method, a generalized network model is developed to simulate evaporation in a porous medium composed of packed spherical beads. The modeling results are in good agreement with the experimental data, particularly in terms of the variation of liquid distribution over time. Our proposed extraction method not only contributes to disclose the structures of pores and corners in real porous media but also benefits the development of generalized network models that can be employed to understand in detail the multiphase transport in porous media from the pore scale perspective.
      [Phys. Rev. Fluids 9, 014303] Published Wed Jan 17, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 014303 (2024)
      PubDate: 2024-01-17T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014303
      Issue No: Vol. 9, No. 1 (2024)
       
  • Cavity dynamics and vibrations of a flexible hydrofoil in the cavitating
           flow

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      Authors: Yunqing Liu; Qin Wu, Hanzhe Zhang, Biao Huang
      First page: 014304
      Abstract: Author(s): Yunqing Liu, Qin Wu, Hanzhe Zhang, and Biao Huang
      This work reveals the mechanism of cavitation-structure interaction by comparing experimental results between a stainless-steel hydrofoil and a flexible hydrofoil, encompassing hydrodynamic loads, cavitation structures, vibrations, and deformations. The hydrodynamic load induces nose-up twisting deformation, which subsequently increases the angle of attack, promoting cavitation inception. Additionally, the dynamics of cloud cavities induced by the shock wave mechanism are clarified based on high-speed images.
      [Phys. Rev. Fluids 9, 014304] Published Tue Jan 23, 2024
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 9, 014304 (2024)
      PubDate: 2024-01-23T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014304
      Issue No: Vol. 9, No. 1 (2024)
       
  • Onset of Lagrangian chaos: From fractal power spectrum to the absolutely
           continuous one

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      Authors: Rafil V. Sagitov; Igor I. Wertgeim, Michael A. Zaks
      First page: 014401
      Abstract: Author(s): Rafil V. Sagitov, Igor I. Wertgeim, and Michael A. Zaks
      We study fluid motions excited by a spatially periodic force in a plane region with periodic boundary conditions; mean drift in both directions across the domain is nonzero. Under weak force, the flow is stationary; Fourier spectra of velocity for advected tracer particles are singular continuous (fractal). At higher amplitudes of the force, the flow pattern periodically oscillates, ensuring the onset of Lagrangian chaos in tracer dynamics. We illustrate the transformation of the power spectrum from the fractal object to the conventional smooth curve (subplots (i-iv)), and describe the accompanying changes in the pattern of autocorrelation for the tracer velocity.
      [Phys. Rev. Fluids 9, 014401] Published Thu Jan 18, 2024
      Keywords: Nonlinear Dynamical Systems
      Citation: Phys. Rev. Fluids 9, 014401 (2024)
      PubDate: 2024-01-18T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014401
      Issue No: Vol. 9, No. 1 (2024)
       
  • Asymmetric Kelvin-Helmholtz instabilities in stratified shear flows

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      Authors: Adam J. K. Yang; Mary-Louise Timmermans, Gregory A. Lawrence
      First page: 014501
      Abstract: Author(s): Adam J. K. Yang, Mary-Louise Timmermans, and Gregory A. Lawrence
      This study elucidates the regime of fluid instabilities that can arise in a stratified shear flow when density and velocity interfaces are not aligned - a common occurrence in various geophysical flows. Through a combination of linear stability analysis and direct numerical simulations, we unveil a hybrid mode characterized by features of both Kelvin-Helmholtz and Holmboe instabilities. By quantifying the crucial role of asymmetry, our findings contribute to a refined understanding of the dynamics and mixing in these stratified shear flows.
      [Phys. Rev. Fluids 9, 014501] Published Tue Jan 02, 2024
      Keywords: Transport and Mixing
      Citation: Phys. Rev. Fluids 9, 014501 (2024)
      PubDate: 2024-01-02T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014501
      Issue No: Vol. 9, No. 1 (2024)
       
  • Dispersion and deformation of molecular patterns written in turbulent air

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      Authors: Willem van de Water; Nico Dam, Enrico Calzavarini
      First page: 014502
      Abstract: Author(s): Willem van de Water, Nico Dam, and Enrico Calzavarini
      This letter “H” is written in turbulent air by tagging molecules in the focus of intense laser beams that cross in space. In the course of 40 microseconds, turbulence deforms and disperses the pattern. It could be used as a way to measure the velocity of the turbulent eddies. However, more importantly, it reveals the intricate interplay between molecular diffusion and turbulent dispersion.
      [Phys. Rev. Fluids 9, 014502] Published Fri Jan 12, 2024
      Keywords: Transport and Mixing
      Citation: Phys. Rev. Fluids 9, 014502 (2024)
      PubDate: 2024-01-12T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014502
      Issue No: Vol. 9, No. 1 (2024)
       
  • Level crossings reveal organized coherent structures in a turbulent time
           series

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      Authors: Subharthi Chowdhuri; Tirtha Banerjee
      First page: 014601
      Abstract: Author(s): Subharthi Chowdhuri and Tirtha Banerjee
      Detection of coherent structures in experiments, when using single-point temporal measurements, poses challenges due to their three-dimensional nature. Past methods, relying on ad hoc thresholds, lacked consistency across studies. To address this, the level-crossing method has been introduced and applied to two datasets of wall-bounded turbulent flows. This method allows the identification of coherent structures in a more objective manner, avoiding the need for arbitrary thresholds. An interesting discovery is that coherent structures influence near-wall turbulence through nonlinear interactions, a phenomenon not discernible through traditional spectral analysis.
      [Phys. Rev. Fluids 9, 014601] Published Wed Jan 17, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 014601 (2024)
      PubDate: 2024-01-17T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014601
      Issue No: Vol. 9, No. 1 (2024)
       
  • Low-order planar pressure reconstruction of stalled airfoils using
           particle image velocimetry data

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      Authors: D. W. Carter; B. Ganapathisubramani
      First page: 014602
      Abstract: Author(s): D. W. Carter and B. Ganapathisubramani
      Structures in turbulent flow are largely responsible for variations in the forces experienced by the body of interest. In this work, the impact of specific structures in the velocity field on the resulting pressure field are revealed using a data-driven framework. The body of interest is a stalled NACA 0012 airfoil obtained from high-resolution large-scale time-resolved particle image velocimetry.
      [Phys. Rev. Fluids 9, 014602] Published Fri Jan 19, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 014602 (2024)
      PubDate: 2024-01-19T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014602
      Issue No: Vol. 9, No. 1 (2024)
       
  • Space-local Navier–Stokes turbulence

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      Authors: Ryo Araki; Wouter J. T. Bos, Susumu Goto
      First page: 014603
      Abstract: Author(s): Ryo Araki, Wouter J. T. Bos, and Susumu Goto
      How local is turbulence' This question has been extensively examined in scale space. In this study, we investigate the locality in physical space by artificially truncating the spatially nonlocal nonlinear interactions and see how the energy cascade is affected by the truncation in three-dimensional turbulence.
      [Phys. Rev. Fluids 9, 014603] Published Tue Jan 23, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 014603 (2024)
      PubDate: 2024-01-23T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014603
      Issue No: Vol. 9, No. 1 (2024)
       
  • Vortex-induced vibration of a flexible pipe under oscillatory sheared flow

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      Authors: Xuepeng Fu; Shixiao Fu, Mengmeng Zhang, Haojie Ren, Bing Zhao, Yuwang Xu
      First page: 014604
      Abstract: Author(s): Xuepeng Fu, Shixiao Fu, Mengmeng Zhang, Haojie Ren, Bing Zhao, and Yuwang Xu
      An experimental apparatus for studying vortex-induced vibration (VIV) of a flexible pipe was designed and constructed in an ocean basin. A VIV test of a tensioned flexible pipe in oscillatory sheared flow (OSF) was performed based on this rotation rig. One end of the test pipe is fixed, and one end is forced to oscillate harmonically with various amplitudes and periods. The results show that VIV under OSF exhibits amplitude modulation and hysteresis phenomena. A critical Keulegan-Carpenter (KC) number is proposed to describe the occurrence of modulated VIV under OSF. The experimental results provide benchmark data for future VIV prediction research.
      [Phys. Rev. Fluids 9, 014604] Published Thu Jan 25, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 014604 (2024)
      PubDate: 2024-01-25T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014604
      Issue No: Vol. 9, No. 1 (2024)
       
  • Study of the wall pressure variations on the stall inception of a thick
           cambered profile at high Reynolds number

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      Authors: Caroline Braud; Bérengère Podvin, Julien Deparday
      First page: 014605
      Abstract: Author(s): Caroline Braud, Bérengère Podvin, and Julien Deparday
      Understanding the flow physics near stall at high chord-based Reynolds numbers (> 106) remains a challenge for both experimental and numerical approaches. Generally statistical bi-dimensionality of the flow is assumed a priori. In the present study, the wall pressure at two chords provides a description of the flow evolution with the angle of incidence. Our results indicate that flow separation at high Reynolds numbers is an inherently local, three-dimensional and unsteady process that occurs in a continuous manner. However, as it can be represented with mainly two proper orthogonal decomposition modes, our results also suggest that a low-order approach may offer a viable modeling route.
      [Phys. Rev. Fluids 9, 014605] Published Fri Jan 26, 2024
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 9, 014605 (2024)
      PubDate: 2024-01-26T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014605
      Issue No: Vol. 9, No. 1 (2024)
       
  • Role of vorticity distribution in the rise and fall of lift during a
           transverse gust encounter

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      Authors: Antonios Gementzopoulos; Girguis Sedky, Anya Jones
      First page: 014701
      Abstract: Author(s): Antonios Gementzopoulos, Girguis Sedky, and Anya Jones
      In this paper, we experimentally investigate the flow fields and lift transients associated with transverse gust encounters. We highlight the key differences between inviscid and viscous gust encounters and discuss how contrasting shed vorticity distributions lead to dissimilar lift behavior during the gust exit. Our findings contribute to a refined understanding of the utility of inviscid models in the prediction of loads during atmospheric gust encounters.
      [Phys. Rev. Fluids 9, 014701] Published Thu Jan 18, 2024
      Keywords: Vortex Dynamics
      Citation: Phys. Rev. Fluids 9, 014701 (2024)
      PubDate: 2024-01-18T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014701
      Issue No: Vol. 9, No. 1 (2024)
       
  • Koopman-based model predictive control with morphing surface: Regulating
           the flutter response of a foil with an active flap

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      Authors: Tso-Kang Wang; Kourosh Shoele
      First page: 014702
      Abstract: Author(s): Tso-Kang Wang and Kourosh Shoele
      In this work, we demonstrated how model predictive control (MPC) can effectively manipulate a highly nonlinear foil-and-flap system to follow designated lift trajectories to sub-5% error. The surrogate model is built through a data-driven method merging fluidic and structural information which can be readily deployed to numerous fluid-structure interaction systems. The rapid optimization procedure utilized to generate the control signal can also be used for estimating ambient environmental change
      [Phys. Rev. Fluids 9, 014702] Published Wed Jan 24, 2024
      Keywords: Vortex Dynamics
      Citation: Phys. Rev. Fluids 9, 014702 (2024)
      PubDate: 2024-01-24T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014702
      Issue No: Vol. 9, No. 1 (2024)
       
  • Wave motions due to a point source pulsating and advancing at forward
           speed parallel to a semi-infinite ice sheet

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      Authors: Z. F. Li; G. X. Wu, Y. Y. Shi
      First page: 014801
      Abstract: Author(s): Z. F. Li, G. X. Wu, and Y. Y. Shi
      In the Arctic region, with the reduction of ice extent and thickness, a shipping route may become possible. We theoretically derive the wave motions induced by a point source pulsating and advancing at the marginal ice zone. It is found that when a ship navigates along the edge of an ice sheet, the free surface wave pattern has two V-shaped components. The outer V-wave is very similar to the common free surface wave without the ice sheet, while the inner V-wave is mainly due to the reflection of the outer V-wave by the ice sheet.
      [Phys. Rev. Fluids 9, 014801] Published Fri Jan 05, 2024
      Keywords: Wave Dynamics, Free Surface Flows, Stratified, and Rotating Flows
      Citation: Phys. Rev. Fluids 9, 014801 (2024)
      PubDate: 2024-01-05T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014801
      Issue No: Vol. 9, No. 1 (2024)
       
  • Gravity current escape from a topographic depression

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      Authors: Edward W. G. Skevington; Andrew J. Hogg
      First page: 014802
      Abstract: Author(s): Edward W. G. Skevington and Andrew J. Hogg
      Density-driven flows climb out of topographic depressions if they are sufficiently energetic. We investigate the inertial dynamics of these unsteady flows theoretically as fluid climbs from a lower to an upper plateau and then simultaneously propagates away from and drains back into the depression. The volume of fluid that escapes the confinement diminishes with a power-law dependence upon time; the draining flow becomes self-similar, and the self-similarity is of the second kind, featuring an exponent which is a function of the frontal Froude number. The volume continues to decrease even when viscous processes are non-negligible and ultimately none of the fluid escapes from the depression.
      [Phys. Rev. Fluids 9, 014802] Published Tue Jan 09, 2024
      Keywords: Wave Dynamics, Free Surface Flows, Stratified, and Rotating Flows
      Citation: Phys. Rev. Fluids 9, 014802 (2024)
      PubDate: 2024-01-09T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014802
      Issue No: Vol. 9, No. 1 (2024)
       
  • Quantifying and predicting near-wall global intermittency in stably
           stratified channel flow

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      Authors: Haoyang Cen; Artem Korobenko, Qi Zhou
      First page: 014803
      Abstract: Author(s): Haoyang Cen, Artem Korobenko, and Qi Zhou
      In this study, we explore the transition from fully developed turbulence to global intermittency in stably stratified channel flow using direct numerical simulations across varying friction Reynolds and shear Richardson numbers. We quantify intermittency by measuring the volume fraction of turbulent patches and find that intermittency can originate from either near-wall or mid-channel regions, depending on the above parameters. The study identifies a critical value of the Nusselt number (approximately 3.0) below which near-wall intermittency consistently occurs. The critical friction Richardson number for intermittency is found to be proportional to the squared Reynolds number.
      [Phys. Rev. Fluids 9, 014803] Published Wed Jan 24, 2024
      Keywords: Wave Dynamics, Free Surface Flows, Stratified, and Rotating Flows
      Citation: Phys. Rev. Fluids 9, 014803 (2024)
      PubDate: 2024-01-24T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.9.014803
      Issue No: Vol. 9, No. 1 (2024)
       
  • Amplitude of water pouring sound

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      Authors: Mouad Boudina; Joonoh Kim, Ho-Young Kim
      First page: L122002
      Abstract: Author(s): Mouad Boudina, Joonoh Kim, and Ho-Young Kim
      The familiar pouring sound we all hear when preparing tea or coffee has been a rare topic of study so far, despite its importance in several applications. We experimentally find that the sound amplitude increases with the jet corrugation, indicating that thin jets are louder than thick ones for the same given height. When pouring from a high distance, the jet breaks up into impacting drops, and the amplitude increases with the jet length and diameter. Results show that the jet corrugation relates to the volume of entrained air, hence the pouring sound can enter as a practical method to measure water aeration rates.
      [Phys. Rev. Fluids 8, L122002] Published Thu Dec 21, 2023
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 8, L122002 (2023)
      PubDate: 2023-12-21T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.L122002
      Issue No: Vol. 8, No. 12 (2023)
       
  • Controlling the dewetting morphologies of thin liquid films by switchable
           substrates

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      Authors: S. Zitz; A. Scagliarini, J. Harting
      First page: L122001
      Abstract: Author(s): S. Zitz, A. Scagliarini, and J. Harting
      Wetting of surfaces holds a crucial interest for diverse technological and societal areas, from nanotechnology to contagion dynamics. We propose the usage of substrates with time-varying wettability as a novel tool to solve a critical problem, namely the control of dewetting morphologies. A new numerical method, able to handle unprecedented system sizes in this context, is employed. We unveil the existence of a droplet-to-rivulet transition determined by the substrate adaptation rate. Our work paves an avenue for the application of simulations to study the complex dynamics of thin liquid films over switchable and adaptive substrates.
      [Phys. Rev. Fluids 8, L122001] Published Tue Dec 19, 2023
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 8, L122001 (2023)
      PubDate: 2023-12-19T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.L122001
      Issue No: Vol. 8, No. 12 (2023)
       
  • Floating wind farm experiments through scaling for wake characterization,
           power extraction, and turbine dynamics

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      Authors: Juliaan Bossuyt; Ondřej Ferčák, Zein Sadek, Charles Meneveau, Dennice F. Gayme, Raúl Bayoán Cal
      First page: 120501
      Abstract: Author(s): Juliaan Bossuyt, Ondřej Ferčák, Zein Sadek, Charles Meneveau, Dennice F. Gayme, and Raúl Bayoán Cal
      A novel scaling methodology is presented for unique wind and water tunnel experiments of floating offshore wind farms. Geometric similarity of the floater design is leveraged to improve the hydraulic response and relax Froude scaling. Turbine motion, power, and wake measurements reveal intricate coupled dynamic interactions between wave topology, wake evolution, turbine response, and wind farm power output.
      [Phys. Rev. Fluids 8, 120501] Published Thu Dec 14, 2023
      Keywords: Invited Articles
      Citation: Phys. Rev. Fluids 8, 120501 (2023)
      PubDate: 2023-12-14T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.120501
      Issue No: Vol. 8, No. 12 (2023)
       
  • Dynamic lift enhancement mechanism of dragonfly wing model by
           vortex-corrugation interaction

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      Authors: Yusuke Fujita; Makoto Iima
      First page: 123101
      Abstract: Author(s): Yusuke Fujita and Makoto Iima
      Dragonfly wings, with their unique corrugated structure, may achieve superior aerodynamic performance in specific flight conditions, although these conditions are not yet fully understood. This led us to investigate the vortex dynamics and lift generation as a corrugated wing transitions from a stationary state to translational motion. The results reveal that suppression of secondary vortices generated on the wing significantly improves the overall performance of corrugated wings. This advances our understanding of flight dynamics and can also contribute to applications in engineering and biomimicry.
      [Phys. Rev. Fluids 8, 123101] Published Thu Dec 07, 2023
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 8, 123101 (2023)
      PubDate: 2023-12-07T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123101
      Issue No: Vol. 8, No. 12 (2023)
       
  • Mean streaming and the onset of turbulence in the reciprocating flow in a
           double bifurcation airway model: Insights for high-frequency ventilation

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      Authors: Chinthaka Jacob; David G. Tingay, Justin S. Leontini
      First page: 123102
      Abstract: Author(s): Chinthaka Jacob, David G. Tingay, and Justin S. Leontini
      This paper reports on a reciprocating flow through a double bifurcation geometry to quantify the potential gas transport in flows similar to those in the human airway during high-frequency ventilation. The roles of nonlinear mean streaming and turbulent diffusion are investigated in appropriate clinical conditions and their dependence on both the upstream and downstream conditions are manifested. We report turbulent bursts occur in the first three generations of the airway when the instantaneous flow velocity exceeds a critical value. Results highlight the importance of considering a model geometry with appropriate complexity for physiological flows.
      [Phys. Rev. Fluids 8, 123102] Published Mon Dec 11, 2023
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 8, 123102 (2023)
      PubDate: 2023-12-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123102
      Issue No: Vol. 8, No. 12 (2023)
       
  • Point torque representations of ciliary flows

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      Authors: Siluvai Antony Selvan; Peter W. Duck, Draga Pihler-Puzović, Douglas R. Brumley
      First page: 123103
      Abstract: Author(s): Siluvai Antony Selvan, Peter W. Duck, Draga Pihler-Puzović, and Douglas R. Brumley
      The beating of cilia and flagella has fascinated biologists and physicists alike for decades. Previous mathematical models designed to capture the corresponding flow fields are typically either highly simplified and do not resolve all lengths scales or are computationally demanding and cannot be easily generalized to larger arrays of cilia. This paper develops an alternative method which uses point torques to represent the cilia and captures the near- and far-field characteristics in an efficient and accurate manner. These singularity solutions can be used to accurately calculate the collective flows and transport properties of larger ciliary arrays.
      [Phys. Rev. Fluids 8, 123103] Published Tue Dec 12, 2023
      Keywords: Biological and Biomedical Flows
      Citation: Phys. Rev. Fluids 8, 123103 (2023)
      PubDate: 2023-12-12T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123103
      Issue No: Vol. 8, No. 12 (2023)
       
  • Premixed flame stability under shear-enhanced diffusion: Effect of the
           flow direction

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      Authors: Joel Daou; Prabakaran Rajamanickam
      First page: 123202
      Abstract: Author(s): Joel Daou and Prabakaran Rajamanickam
      In the presence of shear-enhanced diffusion (Taylor dispersion), flame propagation is effectively anisotropic. The paper clarifies the influence of the direction of a shear flow relative to the direction of propagation on the diffusional-thermal instabilities of premixed flames. Interestingly, the cellular flame instability can now be encountered in mixtures with Lewis numbers larger than one.
      [Phys. Rev. Fluids 8, 123202] Published Mon Dec 11, 2023
      Keywords: Combustion Fluid Mechanics and Reacting Flows
      Citation: Phys. Rev. Fluids 8, 123202 (2023)
      PubDate: 2023-12-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123202
      Issue No: Vol. 8, No. 12 (2023)
       
  • Towards a constitutive relation for emulsions exhibiting a yield stress

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      Authors: H. V. M Kibbelaar; A. Deblais, G. Briand, Y. Hendrix, A. Gaillard, K. P. Velikov, M. M. Denn, D. Bonn
      First page: 123301
      Abstract: Author(s): H. V. M Kibbelaar, A. Deblais, G. Briand, Y. Hendrix, A. Gaillard, K. P. Velikov, M. M. Denn, and D. Bonn
      Many materials encountered around us in daily life are yield stress materials, which behave solid-like for small applied stresses, but start to flow when the applied stress exceeds a threshold. The shear viscosity of these materials is relatively well understood. However, this is far from a complete and satisfactory description of the mechanical response, and most flows are more complicated. A coherent picture for general flows is still lacking.
      [Phys. Rev. Fluids 8, 123301] Published Thu Dec 07, 2023
      Keywords: Complex and Non-Newtonian Fluids
      Citation: Phys. Rev. Fluids 8, 123301 (2023)
      PubDate: 2023-12-07T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123301
      Issue No: Vol. 8, No. 12 (2023)
       
  • Numerical investigation of quasistatic magnetoconvection with an imposed
           horizontal magnetic field

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      Authors: Michael A. Calkins; Talal AlRefae, Angel Hernandez, Ming Yan, Stefano Maffei
      First page: 123501
      Abstract: Author(s): Michael A. Calkins, Talal AlRefae, Angel Hernandez, Ming Yan, and Stefano Maffei
      Buoyancy-driven flow of an electrically conducting fluid occurs in planets, stars and industrial applications. Here we use simulations of Rayleigh-Bénard convection with an imposed horizontal magnetic field and stress-free mechanical boundary conditions as a simplified model for understanding such systems. As the buoyancy forcing and magnetic field strength are increased we find a sequence of bifurcations, ranging from steady two-dimensional convection cells to three-dimensional anisotropic convective turbulence. Large scale mean flows become dominant as the parameters are made more extreme.
      [Phys. Rev. Fluids 8, 123501] Published Mon Dec 11, 2023
      Keywords: Convection
      Citation: Phys. Rev. Fluids 8, 123501 (2023)
      PubDate: 2023-12-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123501
      Issue No: Vol. 8, No. 12 (2023)
       
  • Biglobal analysis of baroclinic instability in a current-undercurrent
           oceanic system

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      Authors: Xianliang Chen; Jianping Gan, James C. McWilliams
      First page: 123801
      Abstract: Author(s): Xianliang Chen, Jianping Gan, and James C. McWilliams
      We study the dynamics of a mesoscale current-undercurrent system motivated from the multilayer circulations in the Western North Pacific, attempting to further understand the dynamic origin of the Luzon Undercurrent. We adopt the so-called biglobal analysis, which can deal with realistic basic flows of continuously nonuniform vertical shear and strong horizontal variation. The high vertical shear between the upper and lower currents, and that near the vertical boundaries give rise to two branches of unstable modes of distinct dynamical features. The interplay between baroclinic and barotropic instabilities, as well as the coupling ageostrophic and viscous/diffusive motions are revealed.
      [Phys. Rev. Fluids 8, 123801] Published Mon Dec 11, 2023
      Keywords: Geophysical, Geological, Urban, and Ecological Flows
      Citation: Phys. Rev. Fluids 8, 123801 (2023)
      PubDate: 2023-12-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123801
      Issue No: Vol. 8, No. 12 (2023)
       
  • Negatively buoyant vortices in the Boussinesq-Euler equations

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      Authors: G. G. Rooney
      First page: 123802
      Abstract: Author(s): G. G. Rooney
      This work investigates an idealized model of a finite-volume, cylindrical gravity current, placing it in a context with non-buoyant dipoles and atmospheric ‘modons’. In cross-section, the current presents as a semicircular vortex of dense fluid in an unstratified background. In the frame traveling with the current, the flow is in a steady-state, achieved by a balanced generation of baroclinic vorticity. Numerical experiments demonstrate how the steadiness of a single vortex depends upon this balance, and show that vortex interactions have similarities to those of solitary waves.
      [Phys. Rev. Fluids 8, 123802] Published Fri Dec 15, 2023
      Keywords: Geophysical, Geological, Urban, and Ecological Flows
      Citation: Phys. Rev. Fluids 8, 123802 (2023)
      PubDate: 2023-12-15T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123802
      Issue No: Vol. 8, No. 12 (2023)
       
  • Experiments on the unsteady massive separation over an aerofoil

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      Authors: S. Mohamed Aniffa; Alakesh Ch. Mandal
      First page: 123901
      Abstract: Author(s): S. Mohamed Aniffa and Alakesh Ch. Mandal
      Instantaneous flow fields over a NACA 0012 aerofoil at the stall and post-stall angles of attack have been measured using the time-resolved particle image velocimetry technique. The time sequence of the measured data reveals that the massive separation over the upper surface of the aerofoil is intermittent in nature. This intermittent massive separation is due to the interchange of instability, that is, from a convective to an absolute instability and from an absolute to a convective instability. A physical mechanism for this intermittent massive separation has also been proposed.
      [Phys. Rev. Fluids 8, 123901] Published Thu Dec 07, 2023
      Keywords: Instability, Transition, and Control
      Citation: Phys. Rev. Fluids 8, 123901 (2023)
      PubDate: 2023-12-07T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123901
      Issue No: Vol. 8, No. 12 (2023)
       
  • Dissolution regimes of a horizontal channel in a gravity field

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      Authors: Wei Guo; Ran Hu, Chen-Xing Zhou, Zhibing Yang, Yi-Feng Chen
      First page: 123902
      Abstract: Author(s): Wei Guo, Ran Hu, Chen-Xing Zhou, Zhibing Yang, and Yi-Feng Chen
      We fabricate a soluble microfluidic channel within a micro-PIV-based imaging system to explore the pore-scale dissolution dynamics in a gravity field. We find that the evolution of eddies induced by buoyancy-driven convection within the flow-dissolution system governs the dissolution rate and the dissolution regimes. This research enhances our comprehension of the interplay between buoyancy-driven convection and forced convection in etching the solid surface.
      [Phys. Rev. Fluids 8, 123902] Published Mon Dec 11, 2023
      Keywords: Instability, Transition, and Control
      Citation: Phys. Rev. Fluids 8, 123902 (2023)
      PubDate: 2023-12-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.123902
      Issue No: Vol. 8, No. 12 (2023)
       
  • Viscous free-surface cusps: Local solution

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      Authors: J. Eggers
      First page: 124001
      Abstract: Author(s): J. Eggers
      In the image, the free surface between a liquid and air is deformed into a sharp cusp by the rapid rotation of the cylinder on the left. We show that such a structure is a generic feature of viscous flow, and study its properties. This is important, since air can enter the fluid through the cusp’s tip, and thus become entrained into the interior of the fluid.
      [Phys. Rev. Fluids 8, 124001] Published Wed Dec 06, 2023
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 8, 124001 (2023)
      PubDate: 2023-12-06T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124001
      Issue No: Vol. 8, No. 12 (2023)
       
  • Prebifurcation enhancement of imbibition-drainage hysteresis cycles

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      Authors: Ido Lavi; Lauren Rose, Ramon Planet, Jaume Casademunt, Stéphane Santucci, Jordi Ortín
      First page: 124002
      Abstract: Author(s): Ido Lavi, Lauren Rose, Ramon Planet, Jaume Casademunt, Stéphane Santucci, and Jordi Ortín
      When flowing through disordered media, fluid-fluid interfaces are subjected to sharp capillary jumps that shape displacements at large scales. The intricacies of this phenomenon are hard to decipher due to the inherent stiffness and non-locality of the problem. Here we use an “imperfect” Hele-Shaw cell to elucidate the response to a single topographical defect as a function of the imposed flow rate, keeping to stable Saffman-Taylor conditions. Through imbibition-drainage experiments and numerical integration of a robust two-dimensional model we showcase the profound impact of the proximity to the fingering instability.
      [Phys. Rev. Fluids 8, 124002] Published Wed Dec 20, 2023
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 8, 124002 (2023)
      PubDate: 2023-12-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124002
      Issue No: Vol. 8, No. 12 (2023)
       
  • Freezing of sessile droplet and frost halo formation

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      Authors: Sivanandan Kavuri; George Karapetsas, Chander Shekhar Sharma, Kirti Chandra Sahu
      First page: 124003
      Abstract: Author(s): Sivanandan Kavuri, George Karapetsas, Chander Shekhar Sharma, and Kirti Chandra Sahu
      Freezing droplets are ubiquitous in many practical applications, like in aircraft and wind turbine icing, spray technologies, food and pharmaceutical engineering, and natural phenomena such as raindrop formation. In the context of sessile droplets, the freezing process unveils fascinating physics, featuring a frost halo on the substrate, the evolution of the liquid-ice interface, and the formation of a cusp-like morphology at the tip of the droplet. Our study explores the novel theoretical aspects of frost halo formation, revealing its intricate link to the inherent evaporation process during the initial freezing phases.
      [Phys. Rev. Fluids 8, 124003] Published Fri Dec 22, 2023
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 8, 124003 (2023)
      PubDate: 2023-12-22T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124003
      Issue No: Vol. 8, No. 12 (2023)
       
  • Dynamic wetting experiments with nitrogen in a quasi-capillary tube

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      Authors: Domenico Fiorini; Alessia Simonini, Johan Steelant, David Seveno, Miguel Alfonso Mendez
      First page: 124004
      Abstract: Author(s): Domenico Fiorini, Alessia Simonini, Johan Steelant, David Seveno, and Miguel Alfonso Mendez
      We perform experiments with liquid nitrogen’s gas-liquid interface oscillations in a U-shaped quartz tube and investigate the wetting dynamics in inertia-dominated conditions. The experiments reveal a linear relationship between dynamic contact angle evolution and Capillary number in advancing conditions while the contact angle remains near equilibrium in receding conditions. An equivalent contact angle, derived from a model, shows the overall independence of the capillary pressure from the actual contact angle evolution. Theoretical analysis indicates viscous forces dominate in small tubes, while gravity and inertial forces govern larger tube oscillations.
      [Phys. Rev. Fluids 8, 124004] Published Thu Dec 28, 2023
      Keywords: Interfacial Phenomena and Flows
      Citation: Phys. Rev. Fluids 8, 124004 (2023)
      PubDate: 2023-12-28T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124004
      Issue No: Vol. 8, No. 12 (2023)
       
  • Tensor network reduced order models for wall-bounded flows

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      Authors: Martin Kiffner; Dieter Jaksch
      First page: 124101
      Abstract: Author(s): Martin Kiffner and Dieter Jaksch
      We introduce a quantum inspired and widely applicable tensor network-based framework for developing reduced order models describing wall-bounded fluid flows. For the examples of the lid-driven and doubly-driven cavities, we find that our method only uses a small fraction of the number of variables parameterizing the solution compared to direct numerical simulation and can improve its runtime by an order of magnitude on comparable hardware. Our work provides a novel path towards efficient high-precision simulations of the Navier-Stokes equation at high Reynolds numbers.
      [Phys. Rev. Fluids 8, 124101] Published Fri Dec 08, 2023
      Keywords: Laminar and Viscous Flows
      Citation: Phys. Rev. Fluids 8, 124101 (2023)
      PubDate: 2023-12-08T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124101
      Issue No: Vol. 8, No. 12 (2023)
       
  • Oscillatory flows in compliant conduits at arbitrary Womersley number

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      Authors: Shrihari D. Pande; Xiaojia Wang, Ivan C. Christov
      First page: 124102
      Abstract: Author(s): Shrihari D. Pande, Xiaojia Wang, and Ivan C. Christov
      Oscillatory flows in deformable tubes have been of intense interest since Womersley’s work in the 1950s. The solutions for the pressure, flow rate, and wave propagation along the tube are a cornerstone of biofluid mechanics. However, it is assumed that the hydrodynamic pressure can only cause infinitesimal wall deformations; the cross-sectional area cannot change. Yet, oscillatory flows do deform conduits to such an extent that a nonlinear pressure gradient develops. We derive and benchmark a reduced-order model (a single, complex-valued partial differential equation for the pressure) that captures two-way coupling between flow and deformation, without restrictions on the oscillation frequency.
      [Phys. Rev. Fluids 8, 124102] Published Wed Dec 20, 2023
      Keywords: Laminar and Viscous Flows
      Citation: Phys. Rev. Fluids 8, 124102 (2023)
      PubDate: 2023-12-20T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124102
      Issue No: Vol. 8, No. 12 (2023)
       
  • Hydrodynamic interactions change the buckling threshold of parallel
           flexible sheets in shear flow

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      Authors: Hugo Perrin; Heng Li, Lorenzo Botto
      First page: 124103
      Abstract: Author(s): Hugo Perrin, Heng Li, and Lorenzo Botto
      Viscous-flow induced buckling modifies the morphology of sheet-like particles suspended in liquids. Experiments reveal that a pair of sheets can bend at a shear rate ten times lower than the buckling threshold defined for a single sheet. Using simulations and modeling, we demonstrate that this softening is due to hydrodynamic interactions. Our study suggests that the morphology of sheet-like particles in suspensions and the resulting rheology is not a purely material property, but also depends on particle concentration and microstructure.
      [Phys. Rev. Fluids 8, 124103] Published Fri Dec 22, 2023
      Keywords: Laminar and Viscous Flows
      Citation: Phys. Rev. Fluids 8, 124103 (2023)
      PubDate: 2023-12-22T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124103
      Issue No: Vol. 8, No. 12 (2023)
       
  • Size of heterogeneous deformations in sheared granular flows

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      Authors: Parisa Shekari; Benjy Marks, Pierre Rognon
      First page: 124301
      Abstract: Author(s): Parisa Shekari, Benjy Marks, and Pierre Rognon
      Granular flows exhibit kinematic patterns reminiscent of turbulence. In discrete element method simulations, we measure the characteristic size of these patterns and relate it to the size of a representative element volume (REV). We find that this size increases and diverges close to jamming. Such large REVs may be the root cause of nonlocal behaviors and finite size effects observed at the continuum level.
      [Phys. Rev. Fluids 8, 124301] Published Fri Dec 08, 2023
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 8, 124301 (2023)
      PubDate: 2023-12-08T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124301
      Issue No: Vol. 8, No. 12 (2023)
       
  • From nearly homogeneous to core-peaking suspensions: Insight in suspension
           pipe flows using MRI and DNS

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      Authors: Willian Hogendoorn; Wim-Paul Breugem, David Frank, Martin Bruschewski, Sven Grundmann, Christian Poelma
      First page: 124302
      Abstract: Author(s): Willian Hogendoorn, Wim-Paul Breugem, David Frank, Martin Bruschewski, Sven Grundmann, and Christian Poelma
      Semi-dilute to dense particle-laden inertial pipe flows are studied using magnetic resonance imaging in conjunction with direct numerical simulations. In general, both methods show an excellent agreement for both the time-averaged velocity and concentration profiles. Different flow regimes are identified based on the experimental and numerical data. For higher solid volume fractions a core-peaking concentration distribution is found that explains the observed drag decrease relative to the drag expected for a uniform concentration distribution.
      [Phys. Rev. Fluids 8, 124302] Published Tue Dec 12, 2023
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 8, 124302 (2023)
      PubDate: 2023-12-12T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124302
      Issue No: Vol. 8, No. 12 (2023)
       
  • Unsteady granular chute flows at high inertial numbers

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      Authors: Satyabrata Patro; Anurag Tripathi, Sumit Kumar, Anubhav Majumdar
      First page: 124303
      Abstract: Author(s): Satyabrata Patro, Anurag Tripathi, Sumit Kumar, and Anubhav Majumdar
      High speed granular flows flowing over inclined surfaces are studied using discrete element method and continuum simulations. Significant slip velocity at the base and strong oscillations in the layer height are observed. The popular inertial-number-based JFP rheological model fails to capture the transient flow dynamics at high inertial numbers. Accounting for the layer dilatancy effect and the presence of normal stress difference is essential to accurately predict the average flow behavior. A modified rheological model recently proposed by the authors, accounting for all these effects describes the evolution of the high-speed granular flow very well for both low as well as high inertial numbers.
      [Phys. Rev. Fluids 8, 124303] Published Tue Dec 26, 2023
      Keywords: Multiphase, Granular, and Particle-Laden Flows
      Citation: Phys. Rev. Fluids 8, 124303 (2023)
      PubDate: 2023-12-26T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124303
      Issue No: Vol. 8, No. 12 (2023)
       
  • Exploring regular and turbulent flow states in active nematic channel flow
           via Exact Coherent Structures and their invariant manifolds

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      Authors: Caleb G. Wagner; Rumayel H. Pallock, Jae Sung Park, Michael M. Norton, Piyush Grover
      First page: 124401
      Abstract: Author(s): Caleb G. Wagner, Rumayel H. Pallock, Jae Sung Park, Michael M. Norton, and Piyush Grover
      Active fluids operating at negligible Reynolds numbers can exhibit spontaneous coherent motion, dynamical vortex patterns, and mesoscale turbulence. We employ tools from nonlinear dynamical systems theory to uncover the global phase space of two-dimensional active nematic channel flow. We compute several Exact Coherent Structures (ECSs), which are exact solutions of the physical dynamics with distinct and regular spatiotemporal structure; examples include unstable equilibria, periodic orbits, and traveling waves. We provide numerical evidence to show that this collection of ECSs and their invariant manifolds act as an organizing template for the complicated spatiotemporal motion of the active fluid.
      [Phys. Rev. Fluids 8, 124401] Published Thu Dec 07, 2023
      Keywords: Nonlinear Dynamical Systems
      Citation: Phys. Rev. Fluids 8, 124401 (2023)
      PubDate: 2023-12-07T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124401
      Issue No: Vol. 8, No. 12 (2023)
       
  • Systematic approach for modeling a nonlocal eddy diffusivity

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      Authors: Jessie Liu; Hannah H. Williams, Ali Mani
      First page: 124501
      Abstract: Author(s): Jessie Liu, Hannah H. Williams, and Ali Mani
      Prior studies have shown that the eddy diffusivities governing mean passive scalar transport can be nonlocal in space and time. However, nonlocal eddy diffusivities are often cost prohibitive to compute and difficult to implement in reduced-order models. This work proposes a systematic and cost-effective approach for quantifying and modeling nonlocal eddy diffusivities.
      [Phys. Rev. Fluids 8, 124501] Published Mon Dec 11, 2023
      Keywords: Transport and Mixing
      Citation: Phys. Rev. Fluids 8, 124501 (2023)
      PubDate: 2023-12-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124501
      Issue No: Vol. 8, No. 12 (2023)
       
  • Study of the vortex structure in compressible wall-bounded turbulence

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      Authors: Tianyi Bai; Cheng Cheng, Kevin P. Griffin, Xinliang Li, Lin Fu
      First page: 124603
      Abstract: Author(s): Tianyi Bai, Cheng Cheng, Kevin P. Griffin, Xinliang Li, and Lin Fu
      Compressible turbulent channel flows exhibit a multitude of vortex structures dispersed throughout the boundary layer. Although the structural similarity between compressible and incompressible flows has been well established, most of these observations are concluded through merely visualizations of instantaneous fields. We dissect the statistical features of vortices in compressible channel flows comprehensively and show a quantitative consistency with incompressible flows by applying semi-local scaling. This work fills a gap in our knowledge about vortex structures in compressible channel flows and first applies Morkovin’s hypothesis to statistics of instantaneous vortex features.
      [Phys. Rev. Fluids 8, 124603] Published Wed Dec 06, 2023
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 8, 124603 (2023)
      PubDate: 2023-12-06T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124603
      Issue No: Vol. 8, No. 12 (2023)
       
  • Reynolds-number effects on the outer region of adverse-pressure-gradient
           turbulent boundary layers

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      Authors: Rahul Deshpande; Aron van den Bogaard, Ricardo Vinuesa, Luka Lindić, Ivan Marusic
      First page: 124604
      Abstract: Author(s): Rahul Deshpande, Aron van den Bogaard, Ricardo Vinuesa, Luka Lindić, and Ivan Marusic
      Reynolds number (Re) effects are studied in the outer region of moderate adverse-pressure-gradient (APG) turbulent boundary layers (TBLs). This study finds that the small scale (viscous) energy in an APG TBL at near-equilibrium conditions reduces with increasing friction Re. The origin of this trend is traced back to the production of turbulent kinetic energy in an APG TBL, the small scale contribution to which is also found to decrease with Re in the outer region. The results emphasize that new scaling arguments and spatial-resolution corrections should be tested rigorously across a broad range of Re, particularly for pressure gradient TBLs.
      [Phys. Rev. Fluids 8, 124604] Published Mon Dec 11, 2023
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 8, 124604 (2023)
      PubDate: 2023-12-11T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124604
      Issue No: Vol. 8, No. 12 (2023)
       
  • Dependence of scalar mixing on initial conditions in turbulent channel
           flow

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      Authors: Milind Singh; Emmanuel Germaine, Laurent Mydlarski, Luca Cortelezzi
      First page: 124605
      Abstract: Author(s): Milind Singh, Emmanuel Germaine, Laurent Mydlarski, and Luca Cortelezzi
      Scalar-field initial conditions can have a strong effect on the evolution(s) of scalar fields and the rate at which mixing occurs. The effects of the scalar field initial conditions are studied by analyzing the evolution of three scalar fields with interfaces oriented normal to the streamwise, wall-normal, and transverse directions. When the interface is aligned normal to the mean velocity vector, higher rates of production and destruction of the scalar dissipation, as well as strong advection and stretching of the interface by the mean flow are observed. It is therefore recommended that scalar interfaces be aligned normal to the mean velocity vector to promote mixing within internal flows.
      [Phys. Rev. Fluids 8, 124605] Published Tue Dec 19, 2023
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 8, 124605 (2023)
      PubDate: 2023-12-19T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124605
      Issue No: Vol. 8, No. 12 (2023)
       
  • A priori screening of data-enabled turbulence models

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      Authors: Peng E. S. Chen; Yuanwei Bin, Xiang I. A. Yang, Yipeng Shi, Mahdi Abkar, George I. Park
      First page: 124606
      Abstract: Author(s): Peng E. S. Chen, Yuanwei Bin, Xiang I. A. Yang, Yipeng Shi, Mahdi Abkar, and George I. Park
      A posteriori validation and verification of black box machine learned turbulence models is time consuming and is not always fruitful. We discuss a theoretical framework that allows a priori screening of machine-learned models that are based on feed-forward neural networks. It requires no knowledge of the weights and bias and only knowledge of the activation function. The method tells one whether a machine learned model preserves basic calibrations like the law of the wall.
      [Phys. Rev. Fluids 8, 124606] Published Thu Dec 21, 2023
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 8, 124606 (2023)
      PubDate: 2023-12-21T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124606
      Issue No: Vol. 8, No. 12 (2023)
       
  • Numerical comparison of two-dimensional Navier-Stokes flows on the whole
           plane and the periodic domain

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      Authors: Koji Ohkitani
      First page: 124607
      Abstract: Author(s): Koji Ohkitani
      A direct numerical comparison is made of two-dimensional Navier-Stokes flows between two different boundary conditions, namely the whole plane and a periodic domain. We study their differences after adjusting the Reynolds number. The norms generally decay faster on the periodic domain than on the whole space. In the case of a simple vortex merger the difference is appreciable, whereas the difference is small in the case of turbulence. This gives support to studying finite-energy turbulence under periodic boundary conditions.
      [Phys. Rev. Fluids 8, 124607] Published Fri Dec 22, 2023
      Keywords: Turbulent Flows
      Citation: Phys. Rev. Fluids 8, 124607 (2023)
      PubDate: 2023-12-22T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124607
      Issue No: Vol. 8, No. 12 (2023)
       
  • Estimates of mode-1 internal tide harmonic generation in the global ocean

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      Authors: Scott Wunsch; F. Joseph Marcellino
      First page: 124801
      Abstract: Author(s): Scott Wunsch and F. Joseph Marcellino
      Internal waves play an important role in the dynamics of the ocean. When propagating in vertically varying stratification, they generate harmonic modes through a nonlinear effect. In this work, measured ocean stratification profiles are analyzed to estimate the propensity of oceanic internal tides to exhibit this effect. As seen in the figure, nonlinear harmonic generation could plausibly occur in the Equatorial Indo-Pacific, but not elsewhere, in the global ocean.
      [Phys. Rev. Fluids 8, 124801] Published Wed Dec 06, 2023
      Keywords: Wave Dynamics, Free Surface Flows, Stratified, and Rotating Flows
      Citation: Phys. Rev. Fluids 8, 124801 (2023)
      PubDate: 2023-12-06T10:00:00+00:00
      DOI: 10.1103/PhysRevFluids.8.124801
      Issue No: Vol. 8, No. 12 (2023)
       
 
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