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Publisher: Springer-Verlag   (Total: 2353 journals)

 Showing 1201 - 1400 of 2353 Journals sorted alphabetically J. of Clinical Geropsychology       (Followers: 1) J. of Clinical Immunology       (Followers: 14, SJR: 1.332, h-index: 75) J. of Clinical Monitoring and Computing       (Followers: 1, SJR: 0.661, h-index: 37) J. of Clinical Psychology in Medical Settings       (Followers: 13, SJR: 0.46, h-index: 34) J. of Cluster Science       (SJR: 0.416, h-index: 31) J. of Coal Science and Engineering (China)       (SJR: 0.188, h-index: 8) J. of Coastal Conservation       (Followers: 7, SJR: 0.474, h-index: 25) J. of Coatings Technology and Research       (Followers: 5, SJR: 0.425, h-index: 25) J. of Combinatorial Optimization       (Followers: 5, SJR: 1.093, h-index: 34) J. of Communications Technology and Electronics       (Followers: 2, SJR: 0.29, h-index: 16) J. of Community Genetics       (Followers: 1, SJR: 0.727, h-index: 14) J. of Community Health       (Followers: 8, SJR: 0.921, h-index: 44) J. of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology       (Followers: 8, SJR: 1.087, h-index: 74) J. of Comparative Physiology B : Biochemical, Systemic, and Environmental Physiology       (Followers: 4, SJR: 1.126, h-index: 59) J. of Compassionate Health Care       (Followers: 2) J. of Computational Analysis and Applications       (SJR: 0.291, h-index: 19) J. of Computational Electronics       (Followers: 4, SJR: 0.511, h-index: 20) J. of Computational Neuroscience       (Followers: 25, SJR: 1.068, h-index: 60) J. of Computer and Systems Sciences Intl.       (SJR: 0.27, h-index: 13) J. of Computer Science and Technology       (Followers: 5, SJR: 0.437, h-index: 31) J. of Computer Virology and Hacking Techniques       (Followers: 6, SJR: 0.151, h-index: 2) J. of Computer-Aided Molecular Design       (Followers: 2, SJR: 0.995, h-index: 78) J. of Computers in Education       (Followers: 11) J. of Computing in Higher Education       (Followers: 13, SJR: 0.363, h-index: 21) J. of Consumer Policy       (Followers: 7, SJR: 0.704, h-index: 30) J. of Contemporary Mathematical Analysis       (SJR: 0.237, h-index: 5) J. of Contemporary Physics (Armenian Academy of Sciences)       (Followers: 11, SJR: 0.197, h-index: 6) J. of Contemporary Psychotherapy       (Followers: 6, SJR: 0.397, h-index: 23) J. of Control Theory and Applications       (Followers: 2, SJR: 0.359, h-index: 19) J. of Control, Automation and Electrical Systems       (Followers: 10, SJR: 0.231, h-index: 9) J. of Crop Science and Biotechnology       (Followers: 7) J. of Cross-Cultural Gerontology       (Followers: 6, SJR: 0.631, h-index: 29) J. of Cryptographic Engineering       (Followers: 5, SJR: 0.989, h-index: 11) J. of Cryptology       (Followers: 3, SJR: 1.443, h-index: 55) J. of Cultural Economics       (Followers: 4, SJR: 0.539, h-index: 29) J. of Database Marketing & Customer Strategy Management       (Followers: 9, SJR: 0.149, h-index: 8) J. of Derivatives & Hedge Funds       (Followers: 8, 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6, SJR: 0.272, h-index: 19) J. of Educational Change       (Followers: 7, SJR: 0.961, h-index: 21) J. of Elasticity       (Followers: 6, SJR: 0.851, h-index: 45) J. of Electroceramics       (SJR: 0.577, h-index: 57) J. of Electronic Materials       (Followers: 5, SJR: 0.609, h-index: 75) J. of Electronic Testing       (Followers: 2, SJR: 0.372, h-index: 27) J. of Electronics (China)       (Followers: 4, SJR: 0.112, h-index: 9) J. of Elementary Science Education       (Followers: 9) J. of Elliptic and Parabolic Equations J. of Engineering Mathematics       (SJR: 0.347, h-index: 37) J. of Engineering Physics and Thermophysics       (Followers: 1, SJR: 0.288, h-index: 11) J. of Engineering Research       (Followers: 1, SJR: 0.145, h-index: 5) J. of Engineering Thermophysics       (Followers: 4, SJR: 0.763, h-index: 9) J. of Environmental Studies and Sciences       (Followers: 2) J. of Ethology       (Followers: 2, SJR: 0.609, h-index: 25) J. of Evolution Equations       (SJR: 0.826, h-index: 26) J. of Evolutionary Biochemistry and Physiology       (SJR: 0.145, h-index: 11) J. of Evolutionary Economics       (Followers: 9, SJR: 0.492, h-index: 52) J. of Experimental and Theoretical Physics       (Followers: 3, SJR: 0.458, h-index: 39) J. of Experimental Criminology       (Followers: 48, SJR: 1.445, h-index: 28) J. of Failure Analysis and Prevention       (Followers: 5, SJR: 0.261, h-index: 15) J. of Family and Economic Issues       (Followers: 6, SJR: 0.396, h-index: 32) J. of Family Violence       (Followers: 38, SJR: 0.639, h-index: 56) J. of Financial Services Marketing       (Followers: 3, SJR: 0.273, h-index: 10) J. of Financial Services Research       (Followers: 24, SJR: 0.572, h-index: 36) J. of Fixed Point Theory and Applications       (SJR: 0.644, h-index: 13) J. of Fluorescence       (Followers: 3, SJR: 0.465, h-index: 56) J. of Food Measurement and Characterization       (SJR: 0.307, h-index: 4) J. of Food Science and Technology       (Followers: 7, 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h-index: 56) J. of Geographical Sciences       (Followers: 1, SJR: 0.8, h-index: 23) J. of Geographical Systems       (Followers: 4, SJR: 0.822, h-index: 39) J. of Geometric Analysis       (Followers: 2, SJR: 1.491, h-index: 27) J. of Geometry       (Followers: 1, SJR: 0.272, h-index: 15) J. of Global Optimization       (Followers: 4, SJR: 0.992, h-index: 60) J. of Global Policy and Governance       (Followers: 11) J. of Grid Computing       (Followers: 1, SJR: 1.414, h-index: 37) J. of Happiness Studies       (Followers: 25, SJR: 0.881, h-index: 39) J. of Hematopathology       (Followers: 4, SJR: 0.2, h-index: 13) J. of Heuristics       (Followers: 5, SJR: 1.308, h-index: 50) J. of High Energy Physics       (Followers: 18, SJR: 1.052, h-index: 153) J. of Homotopy and Related Structures       (SJR: 0.232, h-index: 2) J. of Housing and the Built Environment       (Followers: 8, SJR: 0.648, h-index: 28) J. of Huazhong University of Science and Technology [Medical Sciences]       (SJR: 0.344, h-index: 19) J. of Ichthyology       (Followers: 3, SJR: 0.304, h-index: 10) J. of Immigrant and Minority Health       (Followers: 12, SJR: 0.759, h-index: 37) J. of Inclusion Phenomena and Macrocyclic Chemistry       (Followers: 1, SJR: 0.331, h-index: 46) J. of Indian Council of Philosophical Research J. of Indian Philosophy       (Followers: 12, SJR: 0.127, h-index: 12) J. of Industrial Microbiology and Biotechnology       (Followers: 16, SJR: 0.966, h-index: 80) J. of Industry, Competition and Trade       (Followers: 8, SJR: 0.327, h-index: 15) J. of Infection and Chemotherapy       (Followers: 1, SJR: 0.673, h-index: 46) J. of Information Technology       (Followers: 54, SJR: 1.474, h-index: 55) J. of Information Technology Teaching Cases       (Followers: 9) J. of Infrared, Millimeter and Terahertz Waves       (Followers: 2, SJR: 1.25, h-index: 36) J. of Inherited Metabolic Disease       (Followers: 2, SJR: 1.389, h-index: 77) J. of Inorganic and Organometallic Polymers 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and Oral Surgery       (Followers: 3) J. of Mechanical Science and Technology       (Followers: 6, SJR: 0.589, h-index: 26) J. of Medical and Biological Engineering       (Followers: 1, SJR: 0.387, h-index: 18) J. of Medical Humanities       (Followers: 22, SJR: 0.299, h-index: 18) J. of Medical Systems       (Followers: 1, SJR: 0.717, h-index: 44) J. of Medical Toxicology       (Followers: 6, SJR: 0.874, h-index: 28) J. of Medical Ultrasonics       (Followers: 2, SJR: 0.18, h-index: 13) J. of Medicine and the Person J. of Membrane Biology       (Followers: 2, SJR: 0.738, h-index: 82) J. of Micro-Bio Robotics       (SJR: 0.28, h-index: 3) J. of Microbiology       (Followers: 8, SJR: 0.741, h-index: 43) J. of Mining Science       (Followers: 4, SJR: 0.317, h-index: 16) J. of Molecular Evolution       (Followers: 9, SJR: 0.952, h-index: 108) J. of Molecular Histology       (Followers: 4, SJR: 0.755, h-index: 48) J. of Molecular Medicine       (Followers: 14, SJR: 2.165, h-index: 113) J. 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h-index: 65) J. of Ornithology       (Followers: 24) J. of Orofacial Orthopedics / Fortschritte der Kieferorthopädie       (SJR: 0.574, h-index: 33)
 Environmental Fluid Mechanics   [SJR: 0.585]   [H-I: 29]   [5 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1573-1510 - ISSN (Online) 1567-7419    Published by Springer-Verlag  [2353 journals]
• Flow and drag force around a free surface piercing cylinder for
environmental applications
• Authors: Thomas Ducrocq; Ludovic Cassan; Jacques Chorda; Hélène Roux
Pages: 629 - 645
Abstract: Abstract This paper investigates flows around a free surface piercing cylinder with Froude number F > 0.5 and Reynolds number around Re = 50,000. The aim of this work is to gain a better understanding of the flow behaviour in environmental systems such as fishways. The advances are based upon experimental and numerical results. Several flow discharges and slopes are tested to obtain both subcritical and supercritical flows. The drag force exerted on the cylinder is measured with the help of a torque gauge while the velocity field is obtained using particle velocimetry. For the numerical part, two URANS turbulence models are tested, the k- $$\omega$$ SST and the RNG k- $$\varepsilon$$ models using the OpenFOAM software suite for subcritical cases, and then compared with the corresponding experimental results. With fishways applications in mind, the changes in drag coefficient $$C_d$$ versus Froude number and water depth are studied and experimental correlations proposed. We conclude that the most suitable URANS turbulence model for reproducing this kind of flow is the k- $$\omega$$ SST model.
PubDate: 2017-08-01
DOI: 10.1007/s10652-016-9505-9
Issue No: Vol. 17, No. 4 (2017)

• Identification of evolving interfacial waves by spatial harmonic analysis
• Authors: Meysam Fazeli; Ammar Safaie; Mirmosadegh Jamali
Pages: 647 - 664
Abstract: Abstract This paper is concerned with an analysis of image processing data to identify interfacial waves at the interface between two fluid layers in a laboratory flume. The interfacial waves are excited through a non-linear resonant interaction with a surface wave traveling in a wave flume filled with a two-layer fluid. A spatial harmonic analysis is proposed to extract information about the nonlinear evolution of the constituent waves from the interface oscillation data. The analysis is capable of handling different stages of the resonance in the wave flume and gives accurate and consistent results on time variations of the wave amplitudes. Contrary to a temporal harmonic analysis, the proposed method does not require prescription of a functional form for the amplitude variations. The experimental measurements are compared to the theoretical predictions and available methods. The proposed method provides an efficient solution for detecting these waves and capturing their behaviors.
PubDate: 2017-08-01
DOI: 10.1007/s10652-016-9506-8
Issue No: Vol. 17, No. 4 (2017)

• Ritter’s dry-bed dam-break flows: positive and negative wave
dynamics
• Authors: Oscar Castro-Orgaz; Hubert Chanson
Pages: 665 - 694
Abstract: Abstract Dam-break flood waves are associated with major environmental disasters provoked by the sudden release of water stored in reservoirs. Ritter found in 1892 an analytical solution to the wave structure of an ideal fluid released during an instantaneous dam failure, propagating over initially dry horizontal terrain. This solution, though ideal, hence frictionless, is widely used to test numerical solutions of the Shallow Water Equations (SWE), and as educational tool in courses of fluid mechanics, given that it is a peculiar case of the Riemann problem. However, the real wave structure observed experimentally differs in a major portion of the wave profile, including the positive and negative fronts. Given the importance of an accurate prediction of the dam break wave, the positive and negative wave portions originating from the breaking of a dam with initially dry land on the tailwater reach are revisited in this work. First, the propagation features of the dry-front are investigated using an analytical boundary-layer type model (Whitham/Dressler/Chanson model) constructed matching an (outer) inviscid dynamic wave to an (inner) viscous diffusive wave. The analytical solution is evaluated using an accurate numerical solution of the SWE produced using the MUSCL-Hancock finite-volume method, which is tested independently obtaining the solution based on the discontinuous Galerkin finite-element method. The propagation features of the negative wave are poorly reproduced by the SWE during the initial stages of dam break flows, and, thus, are then investigated using the Serre–Green–Naghdi equations for weakly-dispersive fully non-linear water waves, which are solved using a finite volume-finite difference scheme.
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9512-5
Issue No: Vol. 17, No. 4 (2017)

• Influence of the secondary motions on pollutant mixing in a meandering
open channel flow
• Authors: Ignacio J. Moncho-Esteve; Frederik Folke; Manuel García-Villalba; Guillermo Palau-Salvador
Pages: 695 - 714
Abstract: Abstract This paper presents large eddy simulation of turbulent flow in a meandering open channel with smooth wall and rectangular cross-section. The Reynolds number based on the channel height is 40,000 and the aspect ratio of the cross-section is 4.48. The depth-averaged mean stream-wise velocity agree well to experimental measurements. In this specific case, two interacting cells are formed that swap from one bend to the other. Transport and mixing of a pollutant is analysed using three different positions of release, e.g. on the inner bank, on the outer bank and on the centre of the cross section. The obtained depth-average mean concentration profiles are reasonably consistent with available experimental data. The role of the secondary motions in the mixing processes is the main focus of the discussion. It is found that the mixing when the scalar is released on the centre of the cross-section is stronger and faster than the mixing of the scalar released on the sides. When the position of release is close to a bank side, the mixing is weaker and a clear concentration of scalar close to the corresponding side-wall can be observed in both cases.
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9513-4
Issue No: Vol. 17, No. 4 (2017)

• A stochastic Lagrangian micromixing model for the dispersion of reactive
scalars in turbulent flows: role of concentration fluctuations and
improvements to the conserved scalar theory under non-homogeneous
conditions
• Authors: Andrea Amicarelli; Giovanni Leuzzi; Paolo Monti; Stefano Alessandrini; Enrico Ferrero
Pages: 715 - 753
Abstract: Abstract Several reaction schemes, based on the conserved scalar theory, are implemented within a stochastic Lagrangian micromixing model to simulate the dispersion of reactive scalars in turbulent flows. In particular, the formulation of the reaction-dominated limit (RDL) reaction scheme is here extended to improve the model performance under non-homogeneous conditions (NHRDL scheme). The validation of the stochastic model is obtained by comparison with the available measurements of reactive pollutant concentrations in a grid-generated turbulent flow. This test case describes the dispersion of two atmospheric reactant species (NO and O3) and their reaction product (NO2) in an unbounded turbulent flow. Model inter-comparisons are also assessed, by considering the results of state-of-the-art models for pollutant dispersion. The present validation shows that RDL reaction scheme provides a systematic overestimation (relative error of ca. 85% around the centreline) in computing the local reactant consumption/production rate, whereas the NHRDL scheme drastically reduces this gap (relative error lower than 5% around the centreline). In terms of NO2 production (or reactant consumption), neglecting concentration fluctuations determines overestimations of the product mean of around 100% and a NO2 local production of one order of magnitude higher than the reference simulation. In terms of standard deviations, the concentration fluctuations of both the passive and reactive scalars are generally of the same order of magnitude or up to 1 or 2 orders of magnitudes higher than the corresponding ensemble mean values, except for the background reactant close to the plume edges. The study highlights the importance of modelling pollutant reactions depending on the instantaneous instead of the mean concentrations of the reactants, thus quantifying the role of the turbulent fluctuations of concentration, in terms of scalar statistics (mean, standard deviation, intensity of fluctuations, skewness and kurtosis of concentration, segregation coefficient, simulated reaction rate). This stochastic particle method represents an efficient numerical technique to solve the convection–diffusion equation for reactive scalars and involves several application fields: micro-scale air quality (urban and street-canyon scales), accidental releases, impact of odours, water quality and fluid flow industrial processes (e.g. combustion).
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9516-1
Issue No: Vol. 17, No. 4 (2017)

• One-dimensional modelling of sediment deposition in reservoirs with
sinking streams
• Authors: Xiaofeng Zhang; Yi Hu; Siqiang Wang; Yao Yue
Pages: 755 - 775
Abstract: Abstract It is common in karst regions that rivers are occasionally cut by mountains, resulting in the alternate appearances of open channel flow and pressurized flow. With more and more reservoirs being built in this region, the complicated sediment transport processes of such mixture flow are urgently needed to study. In this paper a one-dimensional numerical model with free surface and pressurized flows coupled together is presented. The simulated results are analyzed to explore deposition process in reservoirs with sinking streams; impacts of different hydraulic conditions on the sedimentation are also studied. To verify the computed results, a flume experiment is also conducted. The results show that deposition of sediments mainly occurs in open channel reaches where the longitudinal profile is similar to that of conventional reservoirs, i.e. typical delta has formed, demonstrating characteristics of deltaic deposition morphology in that the crest of delta moves to the downstream direction over time. The model provided by this paper is not only proved to simulate the characteristics of deposition in karst reservoirs successfully, but also reveal the impacts of hydraulic conditions in such circumstances.
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9517-0
Issue No: Vol. 17, No. 4 (2017)

• Single-column model and large eddy simulation of the evening transition in
the planetary boundary layer
• Authors: G. C. Cuchiara; B. Rappenglück
Pages: 777 - 798
Abstract: Abstract In the present study, the well-known case of day 33 of the Wangara experiment is resimulated using the Weather Research and Forecasting (WRF) model in an idealized single-column mode to assess the performance of a frequently used planetary boundary layer (PBL) scheme, the Yonsei University PBL scheme. These results are compared with two large eddy simulations for the same case study imposing different surface fluxes: one using previous surface fluxes calculated for the Wangara experiment and a second one using output from the WRF model. Finally, an alternative set of eddy diffusivity equations was tested to represent the transition characteristics of a sunset period, which led to a gradual decrease of the eddy diffusivity, and replaces the instantaneous collapse of traditional diagnostics for eddy diffusivities. More appreciable changes were observed in air temperature and wind speed (up to 0.5 K, and 0.6 m s−1, respectively), whereas the changes in specific humidity were modest (up to 0.003 g kg−1). Although the representation of the convective decay in the standard parameterization did not show noticeable improvements in the simulation of state variables for the selected Wangara case study day, small changes in the eddy diffusivity over consecutive hours throughout the night can impact the simulation of distribution of trace gases in air quality models. So, this work points out the relevance of simulating the turbulent decay during sunset, which could help air quality forecast models to better represent the distribution of pollutants storage in the residual layer during the entire night.
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9518-z
Issue No: Vol. 17, No. 4 (2017)

• Penetrative convection in slender containers
• Authors: Suhas U. Pol; Harindra J. S. Fernando
Pages: 799 - 814
Abstract: Abstract An experimental study was conducted to investigate the penetration of a convective mixed layer into an overlying stably (solutally) stratified layer contained in a narrow, tall vessel when the fluid is subjected to a destabilizing heat flux from below. The interest was the evolution of the bottom mixed-layer height ( $$h$$ ) with time ( $$t$$ ) in the presence of side-wall effects, but without the formation of conventional double-diffusive layers. The side-wall effects are expected at small mixed-layer aspect ratios, $$\varGamma_{h} = (W/h)$$ , where $$W$$ is the container width. This case has not been studied hitherto, although there are important environmental and industrial applications. The mixed-layer growth laws for low aspect ratio convection were formulated by assuming a balance between the vertical kinetic energy flux at the interface and the rate of change of potential energy of the fluid system due to turbulent entrainment. The effects of sidewalls were considered using similarity arguments, by taking characteristic rms velocities to be a function of $$\varGamma_{h}$$ , in addition to buoyancy flux ( $$q_{0}$$ ) and $$h$$ . In all stages of evolution, the similarity variables $$\xi = h/W$$ and $$t^{\prime } = Nt/A$$ , where $$A = N^{3} W^{2} /4q_{0}$$ and $$N$$ is the buoyancy frequency, scaled the mixed-layer evolution data remarkably well. Significant wall effects were noted when $$\varGamma_{h} < 1$$ , and for this case the interfacial vertical turbulent velocity and length scales were identified via scaling arguments and experimental data.
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9522-3
Issue No: Vol. 17, No. 4 (2017)

• Hydrodynamics and bed stability of open channel flows with submerged
foliaged plants
• Authors: M. X. Bao; C. W. Li
Pages: 815 - 831
Abstract: Abstract In this work we investigate experimentally and numerically the flow structure around foliaged plants deployed in a channel with gravels on the bed under submerged and barely submerged conditions. Velocity and Reynolds stress were measured by using a NORTEK Vectrino profiler. Visual observation shows that the initial motion of gravels is easier to be triggered under the condition of flow with barely submerged vegetation. This is confirmed by the measured velocity, Reynolds stress and total kinetic energy (TKE) profiles. The velocity exhibits a speed up in the near-bed region, and the associated Reynolds stress and TKE increase there. A 3D numerical model is then verified against the experiments and used to investigate systematically the effect of degree of submergence of foliaged plants on the channel bed shear stress. The results show that the maximum bed shear stress occurs when the foliage is situated slightly below the water surface, which can enhance channel bed instability.
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9524-1
Issue No: Vol. 17, No. 4 (2017)

• Influence of a flooding event discharge on accretion in wetlands
• Authors: T. Serra; A. Ros; C. Vergés; X. Casamitjana
Pages: 833 - 851
Abstract: Abstract Flooding events in wetlands transport sediment particles landwards and can increase accretion in some areas of the wetland or resuspend the sediment in other areas. In this study a flooding event with different water discharges was analyzed in a laboratory simulated wetland to determine the effect stem density has on particle trapping. The discharge that entered the simulated wetland was a particle laden barotropic current that initially produced a pulse that traveled through the wetland. After the first pulse, a baroclinic current, with a different timescale to the initial pulse, developed. Three stem densities, along with the ‘without plant case’, were considered. A semi-empirical model was formulated to explain the propagation of the water pulse. The model predicted the velocity of the pulse dampening in the presence of the simulated vegetation, by using the roughness parameter that had been found to increase with stem density. The baroclinic current propagated at a lower velocity than the pulse did, and its velocity decreased with stem density. As less sediment was found in the wetland with denser canopies, this indicates that the presence of a canopy acts as a barrier to sediment transportation. Furthermore, a greater amount of sediment was deposited in regions at the foot of the denser vegetated wetland zone and the sediment deposition also increased with the water discharge.
PubDate: 2017-08-01
DOI: 10.1007/s10652-017-9528-x
Issue No: Vol. 17, No. 4 (2017)

• Gyre formation in open and deep lacustrine embayments: the example of Lake
Geneva, Switzerland
• Authors: A. M. Razmi; U. Lemmin; D. Bouffard; A. Wüest; R. E. Uittenbogaard; D. A. Barry
Pages: 415 - 428
Abstract: Abstract Numerical simulations were carried out to investigate gyres within open lacustrine embayments subjected to parallel-to-shore currents. In such embayments, gyre formation occurs due to flow separation at the embayment’s upstream edge. High momentum fluid from the mixing layer between the embayment and offshore flows into the embayment and produces recirculating flow. Systematic numerical experiments using different synthetic embayment configurations were used to examine the impact of embayment geometry. Geometries included embayments with different aspect ratios, depths and embayment corner angles. The magnitudes of the recirculation and turbulent kinetic energy (TKE) in the embayment vary significantly for angles in the range 40°–55°. Embayments with corner angles less than 50° have much stronger recirculation and TKE, other parameters remaining the same. The numerical findings are consistent with gyre formation observed in two embayments located in Lake Geneva, Switzerland, and thus help explain flow patterns recorded in lacustrine shoreline regions.
PubDate: 2017-06-01
DOI: 10.1007/s10652-016-9494-8
Issue No: Vol. 17, No. 3 (2017)

• Impact of windage on ocean surface Lagrangian coherent structures
• Authors: Michael R. Allshouse; Gregory N. Ivey; Ryan J. Lowe; Nicole L. Jones; C. J. Beegle-Krause; Jiangtao Xu; Thomas Peacock
Pages: 473 - 483
Abstract: Abstract Windage, the additional direct, wind-induced drift of material floating at the free surface of the ocean, plays a crucial role in the surface transport of biological and contaminant material. Lagrangian coherent structures (LCS) uncover the hidden organizing structures that underlie material transport by fluid flows. Despite numerous studies in which LCS ideas have been applied to ocean surface transport scenarios, such as oil spills, debris fields and biological material, there has been no consideration of the influence of windage on LCS. Here we investigate and demonstrate the impact of windage on ocean surface LCS via a case study of the ocean surrounding the UNESCO World Heritage Ningaloo coral reef coast in Western Australia. We demonstrate that the inclusion of windage is necessary when applying LCS to the study of surface transport of any floating material in the ocean.
PubDate: 2017-06-01
DOI: 10.1007/s10652-016-9499-3
Issue No: Vol. 17, No. 3 (2017)

• Comparison of analytical descriptions of nocturnal low-level jets within
the Ekman model framework
• Authors: Elizabeth Smith; Evgeni Fedorovich; Alan Shapiro
Pages: 485 - 495
Abstract: Abstract This study focuses on the inertial oscillation aspect of the nocturnal low-level jet (NLLJ). In the context of the Ekman model solutions, conceptual NLLJ inertial oscillation analytical frameworks proposed by Blackadar in 1957 and Shapiro and Fedorovich and van de Wiel et al. in 2010 are compared. Considering a NLLJ produced via direct numerical simulation over flat terrain with no baroclinic influence as a reference case, the deficiencies of each framework in representing a realistic NLLJ are assessed. The Blackadar theory results in unrealistic wind profiles near the surface. While extensions of Blackadar’s framework by Shapiro and Fedorovich and van de Wiel et al. produce more realistic NLLJs, the simpler approach taken by van de Wiel et al. does not describe the NLLJ wind hodograph at later times sufficiently in qualitative terms.
PubDate: 2017-06-01
DOI: 10.1007/s10652-016-9502-z
Issue No: Vol. 17, No. 3 (2017)

• LES validation of urban flow, part II: eddy statistics and flow structures
• Authors: Denise Hertwig; Gopal Patnaik; Bernd Leitl
Pages: 551 - 578
Abstract: Abstract Time-dependent three-dimensional numerical simulations such as large-eddy simulation (LES) play an important role in fundamental research and practical applications in meteorology and wind engineering. Whether these simulations provide a sufficiently accurate picture of the time-dependent structure of the flow, however, is often not determined in enough detail. We propose an application-specific validation procedure for LES that focuses on the time dependent nature of mechanically induced shear-layer turbulence to derive information about strengths and limitations of the model. The validation procedure is tested for LES of turbulent flow in a complex city, for which reference data from wind-tunnel experiments are available. An initial comparison of mean flow statistics and frequency distributions was presented in part I. Part II focuses on comparing eddy statistics and flow structures. Analyses of integral time scales and auto-spectral energy densities show that the tested LES reproduces the temporal characteristics of energy-dominant and flux-carrying eddies accurately. Quadrant analysis of the vertical turbulent momentum flux reveals strong similarities between instantaneous ejection-sweep patterns in the LES and the laboratory flow, also showing comparable occurrence statistics of rare but strong flux events. A further comparison of wavelet-coefficient frequency distributions and associated high-order statistics reveals a strong agreement of location-dependent intermittency patterns induced by resolved eddies in the energy-production range. The validation concept enables wide-ranging conclusions to be drawn about the skill of turbulence-resolving simulations than the traditional approach of comparing only mean flow and turbulence statistics. Based on the accuracy levels determined, it can be stated that the tested LES is sufficiently accurate for its purpose of generating realistic urban wind fields that can be used to drive simpler dispersion models.
PubDate: 2017-06-01
DOI: 10.1007/s10652-016-9504-x
Issue No: Vol. 17, No. 3 (2017)

• Numerical and experimental study of sensitivity factors on heat island of
residence community
• Authors: Weixue Cao; Yuying Xue
Abstract: Abstract How to mitigate the effect of the urban heat island has become a hot research problem in the field of the environment, landscape engineering, and the architectural design. The heat island of the micro-climate, such as the residence community, has much more impact on the people’s life, and should be paid more attentions. In this paper, the experiment and simulation methods are combined to study the heat island of residence community. Four sensitivity factors (wind velocity, underlying and building surface, anthropogenic heating and landscape) are chosen to study their influences on the urban heat island (UHI). The results show that the correlation coefficients of the above four sensitivity factors on the UHI are −0.718, 0.521, 0.251 and −0.229, respectively. And the sequence of the above factors to reduce UHI from strong to weak is wind velocity, underlying and the building surface, anthropogenic heating and the landscape.
PubDate: 2017-07-21
DOI: 10.1007/s10652-017-9544-x

• A new model to predict the relative permeability of wetting phase for
tight sandstones
• Authors: Yuhang Guo; Baozhi Pan; Lihua Zhang; Chunhui Fang
Abstract: Abstract As the existing model is not suitable for tight sandstone reservoirs, a new model has been derived theoretically to correlate the relative permeability of wetting phase, saturation and the tortuosity ratio based on revised Kozeny–Carman equation. According to the similarity between the flow of fluid and current, we found that the wetting phase relative permeability is a function of the tortuosity ratio, saturation and the saturation index. In order to verify the new model, 11 cores were taken from tight sandstone reservoirs in northwestern and northeastern China. By comparing with the existing models, the new model is more suitable for the core which has low permeability (<10 mD) and saturation index (<1.8).
PubDate: 2017-07-20
DOI: 10.1007/s10652-017-9543-y

• On dust concentration profile above an area source in a neutral
atmospheric surface layer
• Authors: Zhengping Zhu; Ruifeng Hu; Xiaojing Zheng; Yan Wang
Abstract: Abstract The power law and logarithmic law among others are the most commonly well-known theories for equilibrium mean profile of dust concentration in a neutral atmospheric surface layer. However, these theories are based on the assumption of homogeneity in horizontal (streamwise) direction, thereby the horizontal advection term in the transport equation is neglected. In this study, with the help of a self-similar analytical solution of the two-dimensional steady-state dust transport equation (Chamecki and Meneveau, J Fluid Mech 683:1–26,  2011), we examine the applicabilities of the assumption which the one-dimensional theories are based on. In addition, we also propose an empirical fit of the theory, and good agreements with reference data have been obtained. The new approximate profile can be used as an alternative of the one-dimensional theories in practical applications.
PubDate: 2017-07-12
DOI: 10.1007/s10652-017-9542-z

• Large-eddy simulation of turbulent flow and structures within and above an
idealized building array
• Authors: M. Saeedi; B.-C. Wang
Abstract: Abstract In this research, wall-modeled LES has been performed to investigate turbulent flow in an idealized urban environment comprised of an array of rectangular buildings (MUST array). An inflow condition based on generation of grid turbulence is utilized to mimic the turbulent approaching boundary layer at the inlet of the computational domain. The numerical approach has been validated by comparing the first- and second-order statistical moments of the turbulent flow field against the available water-channel measurement data. Turbulent coherent flow structures, energy spectra, and budget balance of the resolved kinetic energy are investigated. With the aid of the dynamic nonlinear subgrid-scale (SGS) stress model, the backscatter of the kinetic energy from small to large scales of flow motions is also studied. It is found that the scatter of kinetic energy is sensitive to the presence of the building obstacles. As the elevation increases, the ratio of the SGS dissipation rate to the viscous dissipation rate remains stable under the backward scatter condition but varies significantly under the forward scatter condition.
PubDate: 2017-07-01
DOI: 10.1007/s10652-017-9540-1

• Development and validation of a Lagrangian method for 3D turbulent flows
with curvilinear free-surface
• Authors: Mitra Javan; Sharareh Mahmodinia; Hamed Hasani
Abstract: Abstract A numerical model was developed based on a moving grid method for simulating three-dimensional turbulent flows affected by curvilinear free surface. Reynolds-Averaged Navier–Stokes equations with the k–ε turbulence model were solved in non-orthogonal curvilinear coordinates. In the free surface, the kinematic boundary condition was implicitly imposed in the pressure Poisson equation derived from the momentum and continuity equations. The water surface elevation was calculated at each time step without solving additional equations. The developed numerical model was validated using the experimental data of the strongly curved channels and submerged hydraulic jump. The numerical simulation of the flow field and free surface elevation in all cases were compared with the experimental results. The agreement between the simulated and measured results was satisfactory for three-dimensional turbulent flows in the strongly curved channels and submerged hydraulic jump. The secondary flow and dip phenomena were correctly simulated in strongly curved channels. This numerical model could accurately predict steep water surface gradients in a submerged hydraulic jump. The reasonable results of the numerical simulation demonstrate the capability of the presented Lagrangian method in hydraulic engineering applications. This model provides a suitable method for simulating the free surface in engineering and environmental problems.
PubDate: 2017-06-30
DOI: 10.1007/s10652-017-9541-0

• Hydrodynamics and turbulence in emergent and sparsely vegetated open
channel flow
• Authors: Soumen Maji; Debasish Pal; Prashanth R. Hanmaiahgari; Umesh P. Gupta
Abstract: Abstract This present study reports the results of an experimental study characterizing thorough variation of turbulent hydrodynamics and flow distribution in emergent and sparsely vegetated open channel flow. An emergent and rigid sparse vegetation patch with regular spacing between stems along the flow and transverse directions was fixed in the central region of the cross-section of open channel. Experiments were conducted in subcritical flow conditions and velocity measurements were obtained with an acoustic Doppler Velocimetry system. Large variations of the turbulence intensities, Reynolds shear stress, turbulent kinetic energy and vortical motions are found in and around the vegetation patch. At any cross-section through the interior of the vegetation patch, streamwise velocity decreases with increase in streamwise length and the velocity profiles converge from the log-law to a linear profile with increasing slope. Time-averaged lateral and vertical velocities inside the vegetation patch increase with increasing streamwise distance and converge from negative values to positive values. Turbulence intensities interior of the sparse vegetation patch are more than those of without the vegetation patch. Similar to the trend of streamwise velocity profiles inside the vegetation, turbulence intensities and longitudinal-normal Reynolds shear stress profile decreases with streamwise direction. In the interior of the vegetation patch and downstream of the trailing edge, turbulent kinetic energy profiles are exhibiting irregular fluctuations and the maximum values are occurring in the outer layer. Analysis of flow distribution confirms sparse vegetation patch is inducing a serpentine flow pattern in its vicinity. At the leading edge, flow is rushing towards the right hand sidewall, and at the trailing edge, flow is turning to the left hand sidewall. In between the leading and trailing edges, the streamlines are following a zig-zag fashion at varied degree along the streamwise and lateral directions. Immediate upstream of the leading edge and in the interior of the vegetation patch, vortex motion is clearly visible and the vortices are stretched along the width of the channel with streamwise direction.
PubDate: 2017-05-12
DOI: 10.1007/s10652-017-9531-2

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