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  Subjects -> ENGINEERING (Total: 2298 journals)
    - CHEMICAL ENGINEERING (192 journals)
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    - ENGINEERING (1209 journals)
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CIVIL ENGINEERING (192 journals)                     

Showing 1 - 192 of 192 Journals sorted alphabetically
ACI Structural Journal     Full-text available via subscription   (Followers: 17)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 2)
Advances in Civil Engineering     Open Access   (Followers: 36)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 28)
Agregat     Open Access  
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 31)
Architectural Engineering     Open Access   (Followers: 4)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 1)
Archives of Civil Engineering     Open Access   (Followers: 10)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 2)
ATBU Journal of Environmental Technology     Open Access   (Followers: 4)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 6)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 10)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 4)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 4)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 16)
Building & Management     Open Access  
Building and Environment     Hybrid Journal   (Followers: 15)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 15)
Bulletin of Pridniprovsk State Academy of Civil Engineering and Architecture     Open Access   (Followers: 6)
Canadian Journal of Civil Engineering     Hybrid Journal   (Followers: 12)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 11)
Case Studies in Structural Engineering     Open Access   (Followers: 9)
Cement and Concrete Composites     Hybrid Journal   (Followers: 17)
Challenge Journal of Concrete Research Letters     Open Access   (Followers: 2)
Challenge Journal of Structural Mechanics     Open Access   (Followers: 5)
Change Over Time     Full-text available via subscription   (Followers: 2)
Civil and Environmental Engineering     Open Access   (Followers: 7)
Civil And Environmental Engineering Reports     Open Access   (Followers: 6)
Civil and Environmental Research     Open Access   (Followers: 19)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 18)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 10)
Civil Engineering Dimension     Open Access   (Followers: 8)
Civil Engineering Infrastructures Journal     Open Access  
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 268)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 11)
Computers & Structures     Hybrid Journal   (Followers: 36)
Concrete Research Letters     Open Access   (Followers: 6)
Construction Economics and Building     Open Access   (Followers: 2)
Construction Engineering     Open Access   (Followers: 9)
Construction Management and Economics     Hybrid Journal   (Followers: 22)
Construction Science     Open Access   (Followers: 4)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access   (Followers: 2)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal   (Followers: 1)
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 17)
Enfoque UTE     Open Access   (Followers: 4)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 7)
Engineering Structures     Hybrid Journal   (Followers: 13)
Engineering Structures and Technologies     Hybrid Journal   (Followers: 2)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 14)
Environmental Geotechnics     Hybrid Journal   (Followers: 5)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 9)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 16)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access  
Frontiers in Built Environment     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 4)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotechnik     Hybrid Journal   (Followers: 3)
Géotechnique Letters     Hybrid Journal   (Followers: 7)
GISAP : Technical Sciences, Construction and Architecture     Open Access  
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
Indonesian Journal of Urban and Environmental Technology     Open Access  
Indoor and Built Environment     Hybrid Journal   (Followers: 2)
Infrastructure Asset Management     Hybrid Journal   (Followers: 2)
Infrastructures     Open Access  
Ingenio Magno     Open Access   (Followers: 1)
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 22)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 3)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 16)
International Journal of Civil, Mechanical and Energy Science     Open Access   (Followers: 1)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 14)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 9)
International Journal of Geo-Engineering     Open Access   (Followers: 3)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Masonry Research and Innovation     Hybrid Journal   (Followers: 1)
International Journal of Pavement Research and Technology     Open Access   (Followers: 6)
International Journal of Protective Structures     Hybrid Journal   (Followers: 6)
International Journal of Steel Structures     Hybrid Journal   (Followers: 2)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 10)
International Journal of Structural Integrity     Hybrid Journal   (Followers: 2)
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Built Environment     Open Access   (Followers: 4)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 8)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 7)
International Journal Sustainable Construction & Design     Open Access  
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 15)
Journal of Building Engineering     Hybrid Journal   (Followers: 1)
Journal of Building Materials and Structures     Open Access   (Followers: 2)
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 12)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 8)
Journal of Civil Engineering Research     Open Access   (Followers: 6)
Journal of Civil Engineering, Science and Technology     Open Access  
Journal of Civil Society     Hybrid Journal   (Followers: 4)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 4)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 24)
Journal of Construction Engineering     Open Access   (Followers: 7)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 19)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 8)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 4)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 6)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 2)
Journal of Green Building     Full-text available via subscription   (Followers: 11)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 14)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 21)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 5)
Journal of Marine Science and Engineering     Open Access   (Followers: 1)
Journal of Materials and Engineering Structures     Open Access   (Followers: 5)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 10)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 11)
Journal of Performance of Constructed Facilities     Full-text available via subscription   (Followers: 4)
Journal of Pipeline Systems Engineering and Practice     Full-text available via subscription   (Followers: 7)
Journal of Rehabilitation in Civil Engineering     Open Access   (Followers: 3)
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 40)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Sustainable Architecture and Civil Engineering     Open Access   (Followers: 3)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the Civil Engineering Forum     Open Access  
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 4)
Journal of Water and Environmental Nanotechnology     Open Access  
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil dan Perencanaan     Open Access   (Followers: 1)
Konstruksia     Open Access  
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 2)
Latin American Journal of Solids and Structures     Open Access   (Followers: 4)
Materiales de Construcción     Open Access  
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 3)
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 17)
npj Materials Degradation     Open Access  
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 7)
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 2)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 4)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 12)
Proceedings of the Institution of Civil Engineers - Management, Procurement and Law     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Municipal Engineer     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Structures and Buildings     Hybrid Journal   (Followers: 4)
Random Structures and Algorithms     Hybrid Journal   (Followers: 5)
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 7)
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
Road Materials and Pavement Design     Hybrid Journal   (Followers: 11)
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 6)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Selected Scientific Papers - Journal of Civil Engineering     Open Access   (Followers: 3)
Slovak Journal of Civil Engineering     Open Access   (Followers: 2)
Soils and foundations     Full-text available via subscription   (Followers: 5)
Steel Construction - Design and Research     Hybrid Journal   (Followers: 3)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 10)
Structural Concrete     Hybrid Journal   (Followers: 11)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 9)
Structural Engineering International     Full-text available via subscription   (Followers: 12)
Structural Mechanics of Engineering Constructions and Buildings     Open Access  
Structural Safety     Hybrid Journal   (Followers: 7)
Structural Survey     Hybrid Journal  
Structure     Full-text available via subscription   (Followers: 23)
Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance     Hybrid Journal   (Followers: 13)
Structures     Hybrid Journal   (Followers: 1)
Study of Civil Engineering and Architecture     Open Access   (Followers: 9)
Superlattices and Microstructures     Hybrid Journal   (Followers: 2)
Surface Innovations     Hybrid Journal  
Technical Report Civil and Architectural Engineering     Open Access  
Teknik     Open Access  
The IES Journal Part A: Civil & Structural Engineering     Hybrid Journal   (Followers: 6)
The Structural Design of Tall and Special Buildings     Hybrid Journal   (Followers: 6)
Thin Films and Nanostructures     Full-text available via subscription   (Followers: 2)
Thin-Walled Structures     Hybrid Journal   (Followers: 4)
Transactions of the VŠB - Technical University of Ostrava. Construction Series     Open Access   (Followers: 1)
Transportation Geotechnics     Full-text available via subscription   (Followers: 1)
Transportation Infrastructure Geotechnology     Hybrid Journal   (Followers: 8)
Underground Space     Open Access  
Water Science & Technology     Partially Free   (Followers: 25)
Water Science and Technology : Water Supply     Partially Free   (Followers: 22)


Journal Cover Journal of Fluids and Structures
  [SJR: 1.282]   [H-I: 70]   [6 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0889-9746 - ISSN (Online) 1095-8622
   Published by Elsevier Homepage  [3118 journals]
  • Global force and moment in rectangular tanks through a modal method for
           wave sloshing
    • Authors: M. Antuono; C. Lugni
      Pages: 1 - 18
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): M. Antuono, C. Lugni
      Basing on a modal description of the sloshing phenomenon, formulas for the global force and moment acting on two-dimensional rectangular tanks are proposed. These are extensively validated through comparison with experimental data for roll motions at different angles of excitement. Moreover, to extend the applicability of the modal method to the most violent breaking cases, a diffusive variant of the scheme is proposed. This relies on the use of a proper diffusive term in the continuity equation and allows for the overcoming of some numerical issues related to the sloshing dynamics in very shallow waters. Finally, a qualitative description of the interaction between diffusion, dispersion and nonlinearities has been proposed for the present modal scheme, along with a physical interpretation of the diffusive term.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.11.004
      Issue No: Vol. 77 (2017)
  • A coupled BE–FE–BE study for investigating the effect of earthquake
           frequency content and predominant period on seismic behavior of
           base-isolated concrete rectangular liquid tanks
    • Authors: Mohammad Reza Shekari
      Pages: 19 - 35
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): Mohammad Reza Shekari
      Main purpose of this study is to numerically simulate a three-dimensional soil–structure–liquid interaction problem in order to scrutinize the dynamic behavior of base-isolated concrete rectangular tanks under horizontal seismic excitations. It has been deduced that in many earthquakes, the isolation systems reduce the earthquake effects on structures by lengthening their fundamental natural periods against excessive drifts of the superstructure. However, in exceptional cases of the soil stiffness and shaking frequency, the base-isolation systems could have noxious effects. Therefore, the numerical seismic response of rectangular liquid tank system isolated by bilinear bearings is investigated under three real earthquakes with different frequency characteristics in this paper. To this end, finite shell elements for tank wall and boundary elements for liquid and soil are used. Subsequently, fluid–structure–soil equations of motion are coupled with isolator governing equation in the time domain, to gain the whole system response. For different concrete tanks from slender to broad ones, the variations of base forces, sloshing responses, shell radial displacements, and hydrodynamic pressures are illustrated under various system parameters such as the flexibility of the isolation system and the soil properties, to censoriously scrutinize the effects of various system parameters on the utility of the base-isolators. From the analyses, author has concluded that the base-isolation effect is intimately dependent on the earthquake characteristics and may amplify or control the structural responses.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.11.003
      Issue No: Vol. 77 (2017)
  • A numerical investigation of Vortex-Induced Vibration response
           characteristics for long flexible cylinders with time-varying axial
    • Authors: Yuchao Yuan; Hongxiang Xue; Wenyong Tang
      Pages: 36 - 57
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): Yuchao Yuan, Hongxiang Xue, Wenyong Tang
      Vortex-Induced Vibration (VIV) for flexible cylinders is a typical fluid–structure interaction problem, and it becomes more complex when the time-varying axial tension effect is considered. An available force–decomposition model is proposed in this paper to investigate the cross-flow VIV response characteristics with time-varying tension. VIV hydrodynamic forces are all based on forced vibration experimental data, and structural stiffness will be updated at each time step to take the tension variation into account. Firstly, this VIV model is compared against the published experimental results of a small-scale cylinder with constant and time-varying tensions. Next, 60 cases of a long flexible cylinder are designed to investigate the time-varying tension effect comprehensively. Several new phenomena such as amplitude modulation, time-lag, frequency transition, mode jump and multi-frequencies response superposition are captured in the response comparison with the constant tension case. The effects of initial phase, amplitude and frequency of the varying tension are respectively discussed in detail. The Mathieu-type resonance between VIV and time-varying tension excitation is proved existent. The response displacement and strain will enlarge significantly at ω T = 2 ω C T , to which enough attention needs to be paid.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.12.004
      Issue No: Vol. 77 (2017)
  • Inverse method for hydrodynamic load reconstruction on a flexible
           surface-piercing hydrofoil in multi-phase flow
    • Authors: J.C. Ward; C.M. Harwood; Y.L. Young
      Pages: 58 - 79
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): J.C. Ward, C.M. Harwood, Y.L. Young
      An inverse method for reconstruction of the in situ steady-state hydrodynamic load distribution using limited strain measurements is developed and validated on a rectangular, flexible surface-piercing hydrofoil in fully-wetted (FW) and fully-ventilated (FV) flows. The hydrofoil is used as a canonical proxy to more complex hydrodynamic lifting surfaces such as marine propulsors and turbines. The approach involves using a forward fluid–structure interaction (FSI) model to predict the hydroelastic response for given operating conditions. The inverse problem is solved as an optimization problem to determine unknown operating conditions. The forward FSI model consists of a nonlinear lifting line (LL) fluid solver with considerations for free surface, ventilation, and viscous effects, and a solid finite element method (FEM) solver using 1-D beam elements representing the spanwise bending and twisting deformations. The coupled FSI model was validated using data collected during towing tank experiments at the University of Michigan. Predictions of the lift and moment coefficients, as well as spanwise bending and twisting deformations agreed well with experimental results in FW and in FV flows. The inverse problem is formulated as an optimization problem to determine the unknown operating conditions that will minimize the difference between the measured and predicted deformations. To avoid non-uniqueness problems often encountered by inverse problems, a dynamic constraint using the measured wetted natural frequencies was added to help regularize the problem and speed up the solution process. A sequential quadratic programming algorithm was used as the optimizer for the inverse problem. The experimental studies showed that the inverse FSI model accurately determined the unknown operating conditions (angle of attack and immersed aspect ratio) for a given a known flow speed and a limited number of strain measurements in both FW and FV conditions. The converged results were used to reconstruct a 3-D hydrodynamic load distribution on the foil and to predict the cavity shape for FV operating conditions, which were found to agree well with experimental measurements and observations.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.12.001
      Issue No: Vol. 77 (2017)
  • Self-sustaining turbulent wake characteristics in fluid–structure
           interaction of a square cylinder
    • Authors: T.P. Miyanawala; R.K. Jaiman
      Pages: 80 - 101
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): T.P. Miyanawala, R.K. Jaiman
      We present a numerical study on the fluid–structure interaction of a square cylinder at subcritical Reynolds numbers 1400 ≤ R e ≤ 10 , 000 . Variation in spatial and temporal structures during the self-sustaining regeneration cycle are investigated via a three-dimensional Navier–Stokes flow coupled with a freely vibrating square cylinder at relatively low mass ratio. We employ a variational fluid–structure interaction formulation based on the recently developed partitioned iterative scheme and the dynamic subgrid-scale turbulence model. To begin, we assess the response amplitudes, the synchronization regimes and the vortex shedding patterns against the experimental measurements for the flow-induced vibration of a square cylinder at zero incidence angle. Of particular interest is to predict and analyze the synchronization regimes and the associated wake structures for a range of reduced velocity. The vibration of the cylinder provides an avenue for the merging of smaller eddies in the vicinity of the cylinder and there are relatively more clustered spanwise rollers and streamwise ribs as compared to the stationary counterpart. We provide a comparative assessment of Reynolds stress distributions in the near-wake region between the VIV lock-in case and its stationary counterpart. We find that the spatial symmetry of the shearing process in the wake shifts to the temporal symmetry of Reynolds stress when the cylinder is free to vibrate. Consequently, in the vibrating case, the competition between the mean shear growth and damping results in a relatively lower frequency shearing as compared to the stationary cylinder. We introduce a representative control volume in the near-wake region to assess the kinetic energy and enstrophy evolution for the stationary and vibrating configurations. We examine the core reason of the matching of periodic wake frequency with the vibrating cylinder frequency through the development of near-wake flow structures and the kinetic energy evolution. By combining these results with the self-sustained process of coherent vortex structure development, we finally explain the formation of intermediate hairpin-like structures in close proximity to the vibrating cylinder and the absence of them in the stationary cylinder.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.11.002
      Issue No: Vol. 77 (2017)
  • A new analytical approach for modeling the added mass and hydrodynamic
           interaction of two cylinders subjected to large motions in a potential
           stagnant fluid
    • Authors: Romain Lagrange; Xavier Delaune; Philippe Piteau; Laurent Borsoi; José Antunes
      Pages: 102 - 114
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): Romain Lagrange, Xavier Delaune, Philippe Piteau, Laurent Borsoi, José Antunes
      A potential theory is presented for the problem of two moving circular cylinders, with possibly different radii, large motions, immersed in an perfect stagnant fluid. We show that the fluid force is the superposition of an added mass term, related to the time variations of the potential, and a quadratic term related to its spatial variations. We provide new simple and exact analytical expressions for the fluid added mass coefficients, in which the effect of the confinement is made explicit. The self-added mass (resp. cross-added mass) is shown to decrease (resp. increase) with the separation distance and increase (resp. decreases) with the radius ratio. We then consider the case in which one cylinder translates along the line joining the centers with a constant speed. We show that the two cylinders are repelled from each other, with a force that diverges to infinity at impact. We extend our approach to the case in which one cylinder is imposed a sinusoidal vibration. We show that the force on the stationary cylinder and the vibration displacement have opposite (resp. identical) axial (resp. transverse) directions. For large vibration amplitudes, this force is strongly altered by the nonlinear effects induced by the spatial variations of the potential. The force on the vibrating cylinder is in phase with the imposed displacement and is mainly driven by the added mass term. The results of this paper are of particular interest for engineers who need to understand the essential features associated with the vibration of a solid body in a still fluid.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.12.002
      Issue No: Vol. 77 (2017)
  • Effects of attachments on aerodynamic characteristics and vortex-induced
           vibration of twin-box girder
    • Authors: Shujin Laima; Hui Li; Wenli Chen; Jinping Ou
      Pages: 115 - 133
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): Shujin Laima, Hui Li, Wenli Chen, Jinping Ou
      An experimental investigation was carried out on the effects of attachments on the aerodynamic characteristics and vortex-induced vibration (VIV) of a twin-box girder. In the study, the flow pattern, pressure distribution, vortex shedding frequency, and VIV of five models, namely Model A (twin-box girder without attachments), Model B (twin-box girder with handrails and crash barriers), Model C (twin-box girder with handrails, crash barriers, and wind barriers), Model D (twin-box girder with maintenance rails), and Model E (twin-box girder with full ancillaries), are compared with a bare deck in detail. The results demonstrate that, owing to the large leading flow separation induced by the attachments, the flow characteristics and VIVs of the twin-box girder with attachments differ considerably from the bare twin-box girder. Because of the large porous ratio, the handrails and crash barriers exert relatively weak influences on the surface pressure distribution. However, the leading wind barrier and maintenance rail generate large flow separation at the leading edges, resulting in larger pressure fluctuations, a wider wake, and larger scale vortex with lower shedding frequency than that of the bare deck. Furthermore, owing to the large leading flow separation, the vertical VIV induced by the motion-induced vortex in the gap is suppressed. However, a torsional VIV is generated by the large-scale alternately shedding vortex in the wake of the downstream box girder.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.12.005
      Issue No: Vol. 77 (2017)
  • Role of skin friction drag during flow-induced reconfiguration of a
           flexible thin plate
    • Authors: Awan Bhati; Rajat Sawanni; Kaushik Kulkarni; Rajneesh Bhardwaj
      Pages: 134 - 150
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): Awan Bhati, Rajat Sawanni, Kaushik Kulkarni, Rajneesh Bhardwaj
      We investigate drag reduction due to the flow-induced reconfiguration of a flexible thin plate in presence of skin friction drag at low Reynolds Number. The plate is subjected to a uniform free stream and is tethered at one end. We extend existing models in the literature to account for the skin friction drag. The total drag on the plate with respect to a rigid upright plate decreases due to flow-induced reconfiguration and further reconfiguration increases the total drag due to increase in skin friction drag. A critical value of Cauchy number ( C a ) exists at which the total drag on the plate with respect to a rigid upright plate is minimum at a given Reynolds number. The reconfigured shape of the plate for this condition is unique, beyond which the total drag increases on the plate even with reconfiguration. The ratio of the skin friction drag coefficient for a horizontal rigid plate and form drag coefficient for an upright rigid plate ( λ ) determines the critical Cauchy number ( C a c r ). We propose modification in the drag scaling with free stream velocity ( F x ∝ U n ) in presence of the skin friction drag. The following expressions of n are found for 0 . 01 ≤ R e ≤ 1 , n = 4 ∕ 5 + λ ∕ 5 for 1 ≤ C a < C a c r and n = 1 + λ ∕ 5 for C a c r ≤ C a ≤ 300 , where R e is Reynolds number. We briefly discuss the combined effect of the skin friction drag and buoyancy on the drag reduction. An assessment of the feasibility of experiments is presented in order to translate the present model to physical systems.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.12.003
      Issue No: Vol. 77 (2017)
  • Experimental assessment of an active L-shaped tab for dynamic stall
    • Authors: A. Zanotti; G. Gibertini
      Pages: 151 - 169
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): A. Zanotti, G. Gibertini
      An experimental activity was performed on a NACA 23012 pitching airfoil to investigate the effectiveness of an active trailing edge L-shaped tab for deep dynamic stall control. The active control system, based on the use of micro pneumatic actuators, was designed to control the deployment and retraction of the tab along the oscillating cycle. In particular, the tab was designed to behave as a Gurney flap when deployed as its end prong protrudes at the airfoil trailing edge, while in retracted position the tab behaves as a trailing edge flap. The L-shaped tab design presents interesting features to be employed on rotor blades, due to an easier integration at the trailing edge with respect to a deployable Gurney flap. Wind tunnel tests were carried out considering two pitching cycles producing deep dynamic stall regime. Unsteady pressure measurements were performed at the model midspan section to obtain the phase-averaged aerodynamic loads curves. The tests results showed that the deployment of the tab during the upstroke produces a conspicuous increase of lift with respect to the clean airfoil case, corresponding to a higher level of available thrust on the retreating blade. The retraction of the tab before stall onset does not introduce a valuable effect in terms of pitching moment peak reduction with respect to clean airfoil. Moreover, the active control system produces a conspicuous reduction of the negatively-damped portions of the pitching cycles and of the negative aerodynamic damping peak that could account for stall flutter divergence.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.11.010
      Issue No: Vol. 77 (2017)
  • Numerical study of vortex-induced vibrations of a flexible cylinder in an
           oscillatory flow
    • Authors: Bowen Fu; Lu Zou; Decheng Wan
      Pages: 170 - 181
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): Bowen Fu, Lu Zou, Decheng Wan
      The vortex-induced vibrations of a flexible cylinder oscillating harmonically in still water have been numerically simulated using a CFD method based on the strip theory. The algorithm PIMPLE in OpenFOAM is adopted to compute the flow field while the small-displacement Bernoulli–Euler bending beam theory is used to model the cylinder. Two ends of the flexible cylinder are forced to oscillate harmonically. The simulation results have been compared with experimental results and further analyzed. Features such as the hysteresis phenomenon and the build-up–lock-in–die-out cycle are observed in the cross-flow vibration. The in-line vibrations consist of three components, the low-frequency oscillation, the first-natural-frequency vibration during the cylinder reversal, and the second-natural-frequency vibration due to vortex shedding. The butterfly-shaped trajectory has been observed. Detailed wavelet analyses of the vibrations have been given at the end.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.12.006
      Issue No: Vol. 77 (2017)
  • Galloping oscillation of a circular cylinder firmly combined with
           different shaped fairing devices
    • Authors: Hanxu Zheng; Jiasong Wang
      Pages: 182 - 195
      Abstract: Publication date: February 2018
      Source:Journal of Fluids and Structures, Volume 77
      Author(s): Hanxu Zheng, Jiasong Wang
      The galloping oscillation of a circular cylinder combined with different fairing devices is numerically studied. The fairing devices are integrated with a circular cylinder that is supported by a spring and a damper. An unsteady Reynolds-averaged Navier–Stokes (URANS) model corrected with the arbitrary Lagrange Euler (ALE) method is used as the governing model of the fluid flow while the governing equations are solved with a total variation diminishing (TVD) finite volume method (FVM). The SST turbulence model is used. The fluid–structure-interaction (FSI) simulations are performed under the reduced velocities ranging from 3 to 25. The simulation results are validated with the available experimental and numerical results with a short-tail fairing device. The influences of the shapes and the characteristic lengths of the fairing devices on the galloping oscillation are discussed. The shape of the fairing devices are found to influence the vortex shedding patterns in the wake of the flow field while the characteristic length decides the galloping behavior of the cylinder at different reduced velocities. The fairing devices with the smallest characteristic length have the best vibration suppression performance in the present study.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.12.010
      Issue No: Vol. 77 (2017)
  • Model-less forecasting of Hopf bifurcations in fluid-structural systems
    • Authors: Amin Ghadami; Carlos E.S. Cesnik; Bogdan I. Epureanu
      Pages: 1 - 13
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Amin Ghadami, Carlos E.S. Cesnik, Bogdan I. Epureanu
      Predicting critical transitions and post-transition dynamics of complex systems is a unique challenge. In this paper, a novel approach is introduced to forecast Hopf bifurcations and the post-bifurcation dynamics of nonlinear fluid-structural systems. The forecasting method is model-less and uses measurements of the system response collected only in the pre-bifurcation regime. To demonstrate the method, it is applied to a cantilever high aspect ratio wing exposed to gust loads as perturbations. To generate surrogate measurements required for forecasting bifurcations in this large-dimensional complex system, a nonlinear strain-based finite element formulation coupled with unsteady aerodynamics is used to model the fluid–structure interaction. Results show that the method successfully forecasts the linear flutter speed and the amplitude of the limit cycle oscillations that occur in the post-bifurcation regime. The procedure is shown to be time efficient, model-less, and to require only few measurements, which makes the proposed forecasting method a unique tool for nonlinear analysis of complex systems.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.09.005
      Issue No: Vol. 76 (2017)
  • Aeroelastic response and energy harvesting from a cantilevered
           piezoelectric laminated plate
    • Authors: D.M. Tang; E.H. Dowell
      Pages: 14 - 36
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): D.M. Tang, E.H. Dowell
      A new nonlinear computational model and code for a piezoelectric–aeroelastic coupled system has been developed. A cantilevered piezoelectric laminated plate in yawed flow ( β ≤ 9 0 0 ) and inverted yawed flow ( β > 9 0 0 ) with a rotated vortex lattice aerodynamic model and new inextensible beam and plate theory is considered in this computational model. For the linear piezoelectric–aeroelastic model a critical flutter or a divergence phenomenon is found for yaw angles β ≤ 9 0 0 or β > 9 0 0 respectively. The divergence speed is independent of the piezoelectric force. Beyond the linear flutter speed, a limit cycle oscillation (LCO) was found for β ≤ 9 0 0 and a large static deflection has been observed for β > 9 0 0 . The power extraction from the piezoelectric network depends on the LCO amplitude, the LCO mode shape and the resistive load, R, for β ≤ 9 0 0 . As flow velocity and resistive load increase, the power extraction increases. From a power efficiency analysis, the best power efficiency is found for a flag like plate when β = 0 0 . This is because this configuration provides the largest LCO amplitude and the best LCO mode shape with a larger bending curvature.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.09.007
      Issue No: Vol. 76 (2017)
  • Experimental investigation on spatial attitudes, dynamic characteristics
           and environmental conditions of rain–wind-induced vibration of stay
           cables with high-precision raining simulator
    • Authors: Yaojun Ge; Ying Chang; Linshan Xu; Lin Zhao
      Pages: 60 - 83
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Yaojun Ge, Ying Chang, Linshan Xu, Lin Zhao
      Rain–wind-induced vibrations (RWIVs) are one of the most important phenomena affecting the performance of stay cables. The phenomena of RWIVs of cable models were successfully reproduced using a high-precision raining simulator, which has refined control of rainfall intensity and simulation of raindrop size and distribution, through wind tunnel tests considering coupling effects of wind velocity and rain intensity. Some main parameters influencing RWIVs, such as cable inclined angle, wind yaw angle, vibration frequency, vibration damping ratio, wind speed and rainfall intensity, were investigated and compared with those obtained under traditional artificial wind–rain testing conditions. The worst combination of conditions for RWIVs could be determined as two unfavorable environmental states: low wind speeds (2.1 ∼ 6.2 m/s) coupled with high rainfall intensities (50 ∼ 80 mm/h), and high wind speeds (6.9 ∼ 10.7 m/s) coupled with low rainfall intensities (10 ∼ 40 mm/h). Finally, the mechanism of rivulet formation during RWIVs is discussed and some conclusions are given.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.09.006
      Issue No: Vol. 76 (2017)
  • Extension of Lighthill’s slender-body theory to moderate aspect
    • Authors: Zhanle Yu; Christophe Eloy
      Pages: 84 - 94
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Zhanle Yu, Christophe Eloy
      Calculating the fluid forces acting on a moving body at high Reynolds number is crucial in many fluid–structure interaction problems, such as fish swimming or flutter instabilities. To estimate these forces, Lighthill developed the slender-body theory, which assumes a potential flow and an asymptotically small aspect ratio. Yet, it is still unclear whether Lighthill’s theory is still valid for aspect ratios of order one. To address this question, we solve numerically with a panel method the full three-dimensional problem of a rectangular plate deforming periodically in a potential flow. These numerical simulations are used to calculate the pressure jump distribution across the plate for different aspect ratios. We find that numerical simulations and slender-body theory give similar results far from trailing edge. Close to the trailing edge however, there is a discrepancy, which is due to the use of a Kutta condition in the simulations (i.e. no pressure jump at the trailing edge), while, in the slender-body theory, the pressure jump is non zero. We propose a simple extension of Lighthill’s slender-body theory that accounts for this discrepancy. The usefulness of this extension is then discussed and illustrated with a generic fluid–structure interaction problem and with the flag instability problem.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.09.010
      Issue No: Vol. 76 (2017)
  • Control of low Reynolds number flow around an airfoil using periodic
           surface morphing: A numerical study
    • Authors: Gareth Jones; Matthew Santer; George Papadakis
      Pages: 95 - 115
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Gareth Jones, Matthew Santer, George Papadakis
      The principal aim of this paper is to use Direct Numerical Simulations (DNS) to explain the mechanisms that allow periodic surface morphing to improve the aerodynamic performance of an airfoil. The work focuses on a NACA-4415 airfoil at Reynolds number R e c = 5 × 1 0 4 and 0 ° angle of attack. At these flow conditions, the boundary layer separates at x ∕ c = 0 . 42 , remains laminar until x ∕ c ≈ 0 . 8 , and then transitions to turbulence. Vortices are formed in the separating shear layer at a characteristic Kelvin–Helmholtz frequency of S t s = 4 . 9 , which compares well with corresponding experiments. These are then shed into the wake. Turbulent reattachment does not occur because the region of high turbulent kinetic energy (and therefore mixing) is located too far downstream and too far away from the airfoil surface to influence the near-wall flow. The effect of three actuation frequencies is examined by performing the simulations on a computational domain that deforms periodically. It is found that by amplifying the Kelvin–Helmholtz instability mechanism, Large Spanwise Coherent structures are forced to form and retain their coherence for a large part of the actuation cycle. Following their formation, these structures entrain high momentum fluid into the near-wall flow, leading to almost complete elimination of the recirculation zone. The instantaneous and phase averaged characteristics of these structures are analyzed and the vortex coherence is related to the phase of actuation. In order to further clarify the process of reduction in the size of recirculation zone, simulations start from the fully-developed uncontrolled flow and continue for 25 actuation cycles. The results indicate that the modification of airfoil characteristics is a gradual process. As the number of cycles increases and the coherent vortices are repeatedly formed and propagate downstream, they entrain momentum, thereby modifying the near wall region. During this transient period, the separated shear layer approaches the airfoil surface and the size of recirculation region decreases. It takes at least 15 cycles for the flow to develop a repeatable, periodic pattern.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.09.009
      Issue No: Vol. 76 (2017)
  • Evolution of vortex structures over flapping foils in shear flows and its
           impact on aerodynamic performance
    • Authors: Meilin Yu; Bin Wang; Z.J. Wang; Saeed Farokhi
      Pages: 116 - 134
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Meilin Yu, Bin Wang, Z.J. Wang, Saeed Farokhi
      The evolution of vortex structures over flapping NACA0012 foils in shear flows and the corresponding aerodynamic performance are numerically studied using a two dimensional (2D) high-order accurate spectral difference Navier–Stokes flow solver, and further analyzed using the dynamic mode decomposition (DMD) method and vortex theory. Several types of vortex structures over pitching or plunging foils are simulated and analyzed to answer the following questions: (1) how mean flow shear affects the evolution of vortex structures, including both leading and trailing edge vortices, over flapping foils; and (2) how mean flow shear affects the aerodynamic performance under different kinematics. A temporal DMD method is used to analyze vortex structures. It is found that mean flow shear does not modify the dominant temporal frequencies in flow fields, but strong mean flow shear can significantly alter the growth rate, amplitude, and spatial patterns of coherent structures. From simulation results, it is observed that mean flow shear can affect evolution as well as interaction among leading and trailing edge vortices, thus altering the direction of wakes behind flapping foils. The mechanism of shear-induced deflective wakes is explained via qualitative analysis of evolution of simplified vortex street models. Finally, the effects of mean flow shear on aerodynamic performances of flapping foils with different kinematics are studied. By comparing the practical aerodynamic performances with those predicted by the steady aerodynamic theory, it is shown that flapping motion can significantly promote unsteady lift generation in mean flow shear. Furthermore, compared with flapping foils with positive mean angles of attack in a uniform incoming flow, the lift over flapping foils in flows with negative mean flow shear is enhanced without compromising thrust generation.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.09.012
      Issue No: Vol. 76 (2017)
  • The Perfectly Matched Layer absorbing boundary for fluid–structure
           interactions using the Immersed Finite Element Method
    • Authors: Jubiao Yang; Feimi Yu; Michael Krane; Lucy T. Zhang
      Pages: 135 - 152
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Jubiao Yang, Feimi Yu, Michael Krane, Lucy T. Zhang
      In this work, a non-reflective boundary condition, the Perfectly Matched Layer (PML) technique, is adapted and implemented in a fluid–structure interaction numerical framework to demonstrate that proper boundary conditions are not only necessary to capture correct wave propagations in a flow field, but also its interacted solid behavior and responses. While most research on the topics of the non-reflective boundary conditions are focused on fluids, little effort has been done in a fluid–structure interaction setting. In this study, the effectiveness of the PML is closely examined in both pure fluid and fluid–structure interaction settings upon incorporating the PML algorithm in a fully-coupled fluid–structure interaction framework, the Immersed Finite Element Method. The performance of the PML boundary condition is evaluated and compared to reference solutions with a variety of benchmark test cases including known and expected solutions of aeroacoustic wave propagation as well as vortex shedding and advection. The application of the PML in numerical simulations of fluid–structure interaction is then investigated to demonstrate the efficacy and necessity of such boundary treatment in order to capture the correct solid deformation and flow field without the requirement of a significantly large computational domain.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.09.002
      Issue No: Vol. 76 (2017)
  • Computation of long lived resonant modes and the poles of the S-matrix in
           water wave scattering
    • Authors: Michael H. Meylan; Colm Fitzgerald
      Pages: 153 - 165
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Michael H. Meylan, Colm Fitzgerald
      Water wave scattering by variable bathymetry and fixed objects in two-dimensions with particular interest in cases where long-lived resonant, or near-trapping, modes arise is studied. The S-matrix (or scattering matrix), which is derived from the frequency domain solution, is introduced and a numerical scheme to compute the elements for complex frequencies by the analytic extension is given. Various examples of the S-matrix are computed and the importance of the singularities or poles of the S-matrix are highlighted. The time-domain problem is then considered, in particular the fluid motion excited by the scattering of an incident wave packet. The singularity expansion method approximation for the time-dependent solution as a sum over resonant modes is obtained using the poles of the S-matrix. The method is illustrated with some numerical examples.

      PubDate: 2017-10-26T07:04:31Z
      DOI: 10.1016/j.jfluidstructs.2017.10.002
      Issue No: Vol. 76 (2017)
  • An integrated particle model for fluid–particle–structure interaction
           problems with free-surface flow and structural failure
    • Authors: Ke Wu; Dongmin Yang; Nigel Wright; Amirul Khan
      Pages: 166 - 184
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Ke Wu, Dongmin Yang, Nigel Wright, Amirul Khan
      Discrete Element Method (DEM) and Smoothed Particles Hydrodynamics (SPH) are integrated to investigate the macroscopic dynamics of fluid–particle–structure interaction (FPSI) problems. With SPH the fluid phase is represented by a set of particle elements moving in accordance with the Navier–Stokes equations. The solid phase consists of physical particle(s) and deformable solid structure(s) which are represented by DEM using a linear contact model and a linear parallel contact model to account for the interaction between particle elements, respectively. To couple the fluid phase and solid particles, a local volume fraction and a weighted average algorithm are proposed to reformulate the governing equations and the interaction forces. The structure is coupled with the fluid phase by incorporating the structure’s particle elements in SPH algorithm. The interaction forces between the solid particles and the structure are computed using the linear contact model in DEM. The proposed model is capable of simulating simultaneously fluid–structure interaction (FSI), particle–particle interaction and fluid–particle interaction (FPI), with good agreement between complicated hybrid numerical methods and experimental results being achieved. Finally, a specific test is carried out to demonstrate the capability of the integrated particle model for simulating FPSI problems with the occurrence of structural failure.

      PubDate: 2017-11-02T07:27:55Z
      DOI: 10.1016/j.jfluidstructs.2017.09.011
      Issue No: Vol. 76 (2017)
  • Numerical investigation of the behaviour and performance of ships
           advancing through restricted shallow waters
    • Authors: Momchil Terziev; Tahsin Tezdogan; Elif Oguz; Tim Gourlay; Yigit Kemal Demirel; Atilla Incecik
      Pages: 185 - 215
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Momchil Terziev, Tahsin Tezdogan, Elif Oguz, Tim Gourlay, Yigit Kemal Demirel, Atilla Incecik
      Upon entering shallow waters, ships experience a number of changes due to the hydrodynamic interaction between the hull and the seabed. Some of these changes are expressed in a pronounced increase in sinkage, trim and resistance. In this paper, a numerical study is performed on the Duisburg Test Case (DTC) container ship using Computational Fluid Dynamics (CFD), the Slender-Body theory and various empirical methods. A parametric comparison of the behaviour and performance estimation techniques in shallow waters for varying channel cross-sections and ship speeds is performed. The main objective of this research is to quantify the effect a step in the channel topography on ship sinkage, trim and resistance. Significant differences are shown in the computed parameters for the DTC advancing through dredged channels and conventional shallow water topographies. The different techniques employed show good agreement, especially in the low speed range.

      PubDate: 2017-11-02T07:27:55Z
      DOI: 10.1016/j.jfluidstructs.2017.10.003
      Issue No: Vol. 76 (2017)
  • A modal frequency-domain generalised force matrix for the unsteady Vortex
           Lattice method
    • Authors: G. Dimitriadis; N.F. Giannelis; G.A. Vio
      Pages: 216 - 228
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): G. Dimitriadis, N.F. Giannelis, G.A. Vio
      The unsteady Vortex Lattice method is becoming an increasingly popular aerodynamic modelling method for incompressible aeroelastic problems, such as flexible low-speed aircraft, wind turbines and flapping flight. It leads to discrete time aeroelastic state space equations, which must be solved in a time-marching framework. Eigenvalue or singular value decompositions of the discrete time equations can be used in order to perform stability analysis but such procedures must be accompanied by model order reduction because the size of the equations is large. This work proposes a modal frequency domain implementation of the Vortex Lattice method, resulting in a modal generalised force matrix. Model order reduction is implicit in the modal approach and stability analysis can be carried out using industry-standard flutter analysis techniques, such as the p–k method. The approach is validated by comparison to wind tunnel flutter data obtained from rectangular cantilever flat plate wings of different aspect ratios and sweep angles. It is found that the aeroelastic model predictions follow the experimental trends for both flutter speed and frequency but tend to be moderately conservative.

      PubDate: 2017-11-02T07:27:55Z
      DOI: 10.1016/j.jfluidstructs.2017.10.010
      Issue No: Vol. 76 (2017)
  • Numerical simulation of parametric liquid sloshing in a horizontally
           baffled rectangular container
    • Authors: V.S. Sanapala; Rajkumar M; K. Velusamy; B.S.V. Patnaik
      Pages: 229 - 250
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): V.S. Sanapala, Rajkumar M, K. Velusamy, B.S.V. Patnaik
      Liquid sloshing is a problem of serious concern in partially filled tanks. Tank designers must ensure safe margins and develop methodologies to overcome a wide range of plausible situations related to transport, wind, earthquake loads etc. to assess the structural stability. In the present study, numerical simulations are carried out to investigate the sloshing dynamics of a partially filled rectangular container, subjected to vertical harmonic as well as seismic excitations. Unlike horizontal excitation, participation of higher modes is of prime concern in vertical (parametric) excitations. The present study numerically simulates and explores methodologies to control the slosh forces and free surface oscillations with the help of a baffle. Detailed numerical validations are carried out against other experimental and computational studies from the literature. Sloshing dynamics under imposed vertical harmonic excitations was investigated at its first and third modes. Based on a detailed study of transient wave profiles, force and pressure time histories, optimal baffle design was achieved. Optimal position of the baffle and its width are systematically obtained with reference to the quiescent free surface. The effectiveness of this baffle was tested against the well known Bhuj earthquake in India.

      PubDate: 2017-11-02T07:27:55Z
      DOI: 10.1016/j.jfluidstructs.2017.10.001
      Issue No: Vol. 76 (2017)
  • Improved SPH simulation of spilled oil contained by flexible floating boom
           under wave–current coupling condition
    • Authors: Yang Shi; Shaowu Li; Hanbao Chen; Ming He; Songdong Shao
      Pages: 272 - 300
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Yang Shi, Shaowu Li, Hanbao Chen, Ming He, Songdong Shao
      A multi-phase Smoothed Particle Hydrodynamics (SPH) method is developed to model the failure process of a flexible oil boom. An algorithm is proposed based on the dynamic boundary particles (DBPs) for preventing particle disorders of multi-phase fluid particle movement around solid boundary. The improved multi-phase SPH model is firstly validated by the experimental data of a wedge falling into a two-layer oil–water fluid. Then a numerical wave–current flume is established with a piston-type active absorbing wave generator and a circulating current system. The model reliability is validated against the measured vertical profiles of velocity. Simulation of the flexible floating boom movement is implemented by introducing a Rigid Module and Flexible Connector (RMFC) multi-body system. The model is finally applied to the simulation of movement of a flexible floating boom in containing industrial gear oil under the action of combined waves and currents. Good agreements are obtained between the SPH modeling results and the experimental data in terms of the ambient wave–current field, hydrodynamic responses of the floating body and evolution process of the oil slick for the flexible boom. The hydrodynamic responses and containment performances of the flexible floating boom are also compared with those of the rigid one. It is found from both the experimental and numerical results that two vortices of the water phase exist in the front and rear of the boom skirt and the size of the front vortex decreases with increase of the current velocity while the wake vortex is reversed. It is also found that the skirt of the flexible boom has a larger magnitude of swaying and rolling than the rigid one and the maximum quantity of escaped oil of a flexible boom within one wave cycle is about 5% more than a rigid one under the present test conditions.

      PubDate: 2017-11-10T06:22:11Z
      DOI: 10.1016/j.jfluidstructs.2017.09.014
      Issue No: Vol. 76 (2017)
  • Validation of turbulence induced vibration design guidelines in a normal
           triangular tube bundle during two-phase crossflow
    • Authors: Ricardo Álvarez-Briceño; Fabio Toshio Kanizawa; Gherhardt Ribatski; Leopoldo P.R. de Oliveira
      Pages: 301 - 318
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Ricardo Álvarez-Briceño, Fabio Toshio Kanizawa, Gherhardt Ribatski, Leopoldo P.R. de Oliveira
      The present paper addresses an experimental investigation on flow-induced vibration for air–water flow across a normal triangular tube bundle, with transverse pitch-to-diameter ratio of 1.26, aiming to validate the design guidelines found in the open literature for turbulence-induced vibration. In order to do so, the present experimental approach features a tube mounted in cantilever, instrumented with two accelerometers, perpendicularly aligned, mounted in the free tip. This configuration allows to measure the tube acceleration response under distinct operation conditions. The dynamic parameters necessary to evaluate the design guidelines are extracted from these data. Assuming that turbulence-induced is the dominant vibration mechanism for the range of experimental conditions covered by the present study, the current models used to predict the tube vibration upper bound are reviewed and implemented. The present results are plotted with these envelopes showing good agreement, hence, validating the test bench for future works. Moreover, it is noticed that the loading patterns are strongly dependent on the experimental conditions, specially the local flow pattern. Additionally, a predictive method for tube displacement amplitude is proposed based on the experimental results obtained in the present study.

      PubDate: 2017-11-10T06:22:11Z
      DOI: 10.1016/j.jfluidstructs.2017.10.013
      Issue No: Vol. 76 (2017)
  • Experimental investigation of flow over a square cylinder with an attached
           splitter plate at intermediate reynolds number
    • Authors: Manish Kumar Chauhan; Sushanta Dutta; Bhupendra Singh More; Bhupendra Kumar Gandhi
      Pages: 319 - 335
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Manish Kumar Chauhan, Sushanta Dutta, Bhupendra Singh More, Bhupendra Kumar Gandhi
      The present work is an experimental investigation of flow control over a square cylinder using an attached splitter plate. The experiments are mainly conducted at a Reynolds number of 485. A splitter plate of varying length from 0 to 6 times of the cylinder width is attached to the rear side of the square cylinder to control the flow. The thickness of the splitter plate is kept constant at 10% of cylinder width. The flow interference of a square cylinder with an attached splitter plate is observed using PIV, Hot wire and flow visualization techniques. The primary focus is given on the flow structure and related forces. From the experiments, it has been observed that a secondary vortex appears at the tail edge of the plate after a particular length of the splitter plate. This vortex rotation is opposite to the main vortex and it influences the primary vortex shedding as well as shear layer formation. As a result, the plate modifies the wake size and flow structure behind the cylinder. The drag coefficient and the Strouhal number decrease with an increase in splitter plate length. A correlation is found between the splitter plate length, Reynolds number, and the drag coefficient. The effect of the splitter plate length on the flow field is also studied in terms of velocity, vorticity, streamlines, recirculation length, and turbulence statistics.

      PubDate: 2017-11-10T06:22:11Z
      DOI: 10.1016/j.jfluidstructs.2017.10.012
      Issue No: Vol. 76 (2017)
  • Interaction of a spark-generated bubble with a two-layered composite beam
    • Authors: S.W. Gong; S.W. Ohl; E. Klaseboer; B.C. Khoo
      Pages: 336 - 348
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): S.W. Gong, S.W. Ohl, E. Klaseboer, B.C. Khoo
      This paper deals with interaction between a spark-generated bubble and a two-layered composite beam (constrained at its two ends) which consists of an aluminum sheet coated by an elastic layer. Both numerical and experimental approaches are employed to investigate the dynamics of bubble collapse near the two-layered composite beam. A good agreement between the numerical simulation and experimental observation is achieved, which reveals that the bubble collapse time is greatly influenced by the nearby two-layered composite beam. The numerical model is then extended to examine the dynamic response of the two-layered composite beam induced by the bubble growth and collapse; and also to explore the correlation between the energy density of the two-layered composite beam and its coating layer stiffness. The results from this study may provide some insights on the protection of submerged marine structures exposed to bubble collapse arising from an underwater explosion.

      PubDate: 2017-11-10T06:22:11Z
      DOI: 10.1016/j.jfluidstructs.2017.09.008
      Issue No: Vol. 76 (2017)
  • A parametric study of Limit Cycle Oscillation of a bladed disk caused by
           flutter and friction at the blade root joints
    • Authors: M. Lassalle; C.M. Firrone
      Pages: 349 - 366
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): M. Lassalle, C.M. Firrone
      The purpose of this paper is the parametric study of the non-linear aero-elastic phenomena of a bladed disk for aeronautical applications in the presence of friction contacts using a one-way coupled method. The calculation is performed using a method based on the Harmonic Balance Method (HBM) and the balance between the energy introduced by the unsteady aerodynamics on the blade airfoil and the dissipative energy. The HBM method is preferred with respect to the Direct Time Integration (DTI) for the strong reduction of the computation time that HBM technique allows in spite of an acceptable level of approximation when nonlinearities are introduced and the response is periodic. The nonlinearity is introduced by purposely developed contact elements, placed at the blade root-joints, that produce additional stiffening and damping in the system due the introduction of contact stiffness and friction forces based on Coulomb’s law. The aero-elastic equilibrium will be investigated through a sensitivity analysis of the Limit Cycle Oscillations (LCO) of the system. The effect of such variations will be highlighted in order to demonstrate what are the parameters that influence most the blade amplitude, both for the CFD and the mechanical simulation. In particular, the uncertainty in the definition of the contact parameters at the blade root will be taken into account by varying the friction coefficient and the normal force distribution on the blade joint. Finally, the results of the analysis will be compared with the experimental data produced with a cold-flow test rig to verify if the sensitivity study associated to the simplifications introduced in the method are compatible with the measured response.

      PubDate: 2017-11-17T07:12:21Z
      DOI: 10.1016/j.jfluidstructs.2017.10.004
      Issue No: Vol. 76 (2017)
  • Flow-induced vibration of three unevenly spaced in-line cylinders in
    • Authors: Mahmoud Shaaban; Atef Mohany
      Pages: 367 - 383
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Mahmoud Shaaban, Atef Mohany
      The flow over three cylinders arranged in-line with uneven spacing in cross-flow is numerically investigated at a Reynolds number of 200. The center-to-center distance between the upstream and the most downstream cylinder was kept constant at 4 diameters. The distance between the inline centers of the upstream and middle cylinders ( x ) was studied in the range of 1.05 to 2.95 diameters. The flow structure around the cylinders shows two distinctive patterns of vortex shedding, one of which occurs at x = 1 . 60 and 1.80 diameters, and causes significantly higher oscillating lift and mean drag forces with a lower value of Strouhal number. At these middle cylinder locations, the shear layer reattaches on the downstream cylinder and results in vortex formation in the gap between the middle and downstream cylinders. On the other hand, at all other locations of the middle cylinder the shear layer does not reattach on the downstream cylinder. Moreover, when the middle cylinder is located at x = 1 . 60 or 1.80 diameters, the vortex formation length is shorter and the vorticity in the downstream vortex street is higher than the case when the middle cylinder is located at all other locations. To understand the effect of these distinctive flow features on the flow-induced vibration response of the most downstream cylinder, the coupling between the flow field and the cylinder motion is numerically modeled. As the reduced velocity is increased, the oscillation amplitude of the downstream cylinder increases to its maximum at lock-in, then it starts to decrease similar to the case of a single cylinder. However, the oscillation amplitude reaches a higher value than that observed for the case of vortex-induced vibration of both a single cylinder and two tandem cylinders. Moreover, significant oscillation amplitude is pertained at high reduced velocities with dependency on the uneven spacing between the cylinders. The frequency of oscillations increases at different rates in three different ranges of reduced velocities, indicating different energy transfer mechanisms. Although the frequency of vibration is shifted away from the structure resonance frequency at high reduced velocities, the significant amplitude of oscillations is attributed to the interaction of two opposing mechanisms that occur when the cylinder is at different positions in the cycle. The wide range of reduced velocities at which the cylinder vibrates with a significant amplitude makes the configuration of three in-line cylinders a good candidate for flow energy harvesting.

      PubDate: 2017-11-17T07:12:21Z
      DOI: 10.1016/j.jfluidstructs.2017.10.007
      Issue No: Vol. 76 (2017)
  • The influence of fish on the mooring loads of a floating net cage
    • Authors: Zhao He; Odd Magnus Faltinsen; Arne Fredheim; Trygve Kristiansen
      Pages: 384 - 395
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Zhao He, Odd Magnus Faltinsen, Arne Fredheim, Trygve Kristiansen
      The influence of fish on the mooring loads of a floating net cage is studied numerically and experimentally. Two experimental series were conducted. One case was model tests with artificial fish. Nine rigid fish models with total volume of 2.5% of the fish cage at rest were placed inside the net cage without touching the net and towed with the net cage. The other case was live fish experiments in waves and current where more than 800 salmons of length 16 cm occupied about 2.5% of the fish cage volume at rest. The flow-displacement effect of a rigid fish in current was simulated by a potential-flow slender-body theory. Viscous wake effects were added. The displacement flow is clearly more important than the viscous wake flow. Both the numerical simulations and the model tests with rigid fish in current show that the fish influence on the mooring loads of the fish cage is less than 3% of the mooring load without fish. However, the measured mooring loads with live fish in current are between 10% and 28% larger than without fish. The reason is contact between the fish and the net cage. Accounting for the latter fact in the numerical model by changing the local solidity ratio of the net in the contact area gave reasonable numerical predictions. The experiments in waves and combined waves and current also showed a non-negligible influence of the fish on the mooring loads. The waves influenced the behaviour of the fish and some of the fish went to the net bottom possibly due to that they were uncomfortable in the wave zone.

      PubDate: 2017-11-17T07:12:21Z
      DOI: 10.1016/j.jfluidstructs.2017.10.016
      Issue No: Vol. 76 (2017)
  • A combined system of tuned immersion mass and sloshing liquid for
           vibration suppression: Optimization and characterization
    • Authors: Xun Xu; Tao Guo; Guojun Li; Guangpu Sun; Binbin Shang; Zhicheng Guan
      Pages: 396 - 410
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Xun Xu, Tao Guo, Guojun Li, Guangpu Sun, Binbin Shang, Zhicheng Guan
      Tuned liquid dampers (TLDs) and tuned mass dampers (TMDs) have been widely used in suppression of structural vibrations. However, the combination of TLDs and TMDs has been rarely investigated. This paper proposes a new vibration suppression system that combines sloshing liquid with tuned mass immerged in it. The vibration attenuation process of the combined system without structure damping is numerically simulated and characterized by using an implicit coupling approach of segregated solvers. The simulation results indicate that the proposed system, tuned immersion mass with liquid damper (TIMLD), can dissipate energy with liquid sloshing while maintaining the energy absorbing capacity of the mass by resonance. Thus, it exhibits a better vibration suppressing performance than conventional vibration suppression systems such as TLD and TMD. The energy absorbing capacity of the combined system with sloshing liquid is much better than that with liquid filled fully. Distinguishing liquid free sloshing frequency significantly from vibration frequency helps the mass to maintain its energy absorbing capacity by resonance. Affected by the resonant structure and excited by the mass, liquid sloshing can dissipate energy significantly, which constitutes the mechanism of vibration suppression of this proposed system. In light of this mechanism and in an attempt to guarantee the mass resonance and to increase the energy dissipation of the liquid, the combined system has been optimized and characterized.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.10.011
      Issue No: Vol. 76 (2017)
  • Coupling analysis between vessel motion and internal nonlinear sloshing
           for FLNG applications
    • Authors: Dongya Zhao; Zhiqiang Hu; Gang Chen; Xiaobo Chen; Xingya Feng
      Pages: 431 - 453
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Dongya Zhao, Zhiqiang Hu, Gang Chen, Xiaobo Chen, Xingya Feng
      The coupling interaction between vessel motions and internal tank sloshing is of vital importance for Floating Liquefied Natural Gas (FLNG) system design and operation due to the exposure to diverse sea states at any filling level. A numerical code based on potential flow is developed in this study to investigate the coupling interaction between 6 degrees of freedom (DOF) vessel motions and internal nonlinear sloshing. The impulsive response function (IRF) method is adopted in the resolution for the 6 DOF vessel motions, and internal liquid sloshing is numerically solved with the boundary element method (BEM). The coupling interaction between vessel motions and internal sloshing is calculated in the time domain through an iteration strategy. For the purpose of validating the code and enabling a perceptual understanding of these coupling effects, experimental tests of a vessel with two rectangular tanks are conducted. The proposed code is also validated by previous numerical and experimental results. In addition, the coupling interaction characteristics of internal liquid sloshing and vessel motions are studied, and the sensitivities of coupling effects to filling levels and wave directions are also analyzed. Decreased natural roll motion frequency and response amplitude are excited in the liquid loading condition more than in the solid loading condition; sway motion has a decreased response in the natural sloshing frequency and a response peak in the frequency region that is higher than the natural sloshing frequency; heave motion is not sensitive to sloshing loads. Phase shift analysis reveals that phase shifts between the wave and the sloshing loads change rapidly near the natural roll frequency and natural sloshing frequency. Furthermore, the natural sloshing frequency varies with changes in the filling level, and the coupling effects become obvious when the natural sloshing frequency is close to main response frequency region of the vessel. Moreover, coupling effects under head wave conditions have similar properties to those under beam sea conditions, but the sensitivity of pitch motion to sloshing is much lower than that of roll motion.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.10.008
      Issue No: Vol. 76 (2017)
  • Numerical simulations of the flow around a square pitching panel
    • Authors: Utku Senturk; Alexander J. Smits
      Pages: 454 - 468
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Utku Senturk, Alexander J. Smits
      Three-dimensional CFD simulations of a rigid, square panel pitching about its leading edge were performed by solving the governing equations in a non-inertial reference frame moving with the body using a solver developed under the OpenFOAM environment. The accuracy of the code is established by comparisons with experiment and DNS. The solver is then used to study the three-dimensional flow field around a rigid propulsor with a square planform pitching about its leading edge. The simulations span the range 500 < R e < 16000 and 0 . 1 < S t < 1 . 0 . Thrust and efficiency characteristics are determined with a peak efficiency of η ≈ 10 % at S t = 0 . 4 and R e = 16000 . The thrust is dependent of Reynolds number for R e ≤ 8000 , and although the efficiency is more sensitive to Reynolds number, for R e > 8000 there is only a weak dependence. By examining the pressure and shear stress distributions on the panel, the dominant contribution to the thrust is found to be the segment of the panel corresponding to the interval 0 . 625 c − 0 . 75 c . The leading and trailing edges are found to generate drag in most cases. Wake visualizations help to identify the wake state and to understand the vortex formation on the panel edges.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.11.001
      Issue No: Vol. 76 (2017)
  • Determination of the normal fluid load on inclined cylinders from optical
           measurements of the reconfiguration of flexible filaments in flow
    • Authors: Jorge Silva-Leon; Andrea Cioncolini; Antonio Filippone
      Pages: 488 - 505
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Jorge Silva-Leon, Andrea Cioncolini, Antonio Filippone
      Reconfigured flexible filaments exposed to steady fluid load were investigated using a novel non-contact optical technique to measure the normal fluid force due to the fluid loading on inclined cylinders for Reynolds numbers from 25 to 460: a range not covered in previous studies that is of relevance in drag reduction and energy harvesting applications. The ranges of the buoyancy number and the Cauchy number covered in the tests were 3 . 6 × 1 0 4 ≤ B ≤ 2 . 1 × 1 0 6 and 7 . 6 × 1 0 4 ≤ C a ≤ 1 . 4 × 1 0 7 . These newly generated data were then used to assess and extend the validity of existing prediction methods for the normal fluid force at low Reynolds numbers. New prediction methods for the equilibrium inclination angle and for the fluid dynamics load were developed for small Reynolds number applications, based on extrapolating existing theoretical results for marine vegetation.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.10.009
      Issue No: Vol. 76 (2017)
  • Coupled motion of two side-by-side inverted flags
    • Authors: Cecilia Huertas-Cerdeira; Boyu Fan; Morteza Gharib
      Pages: 527 - 535
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Cecilia Huertas-Cerdeira, Boyu Fan, Morteza Gharib
      The interaction and coupling between two inverted flags that are placed side-by-side in a uniform flow is investigated in an effort to determine the behavior of systems that are formed by arrays of cantilevered plates. Inverted flags are elastic plates that are free to move at their leading edge and clamped at their trailing edge. We show that placing two inverted flags of equal dimensions side-by-side will cause their motion to couple. In-phase, anti-phase, staggered, alternating and decoupled flapping modes are present, with the anti-phase mode being predominant at small flag distances and low wind speeds. Increases both in amplitude and frequency of flapping are observed in the two flag system with respect to a single flag. Two side-by-side inverted flags of different lengths are found to interact for small length differences, with the longer flag being able to induce a motion on the shorter flag even when the latter is outside of its flapping wind speed range.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.11.005
      Issue No: Vol. 76 (2017)
  • Control of flow separation around an airfoil at low Reynolds numbers using
           periodic surface morphing
    • Authors: G. Jones; M. Santer; M. Debiasi; G. Papadakis
      Pages: 536 - 557
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): G. Jones, M. Santer, M. Debiasi, G. Papadakis
      The paper investigates experimentally the low Reynolds number flow ( R e c = 50 , 000 ) around a model that approximates a NACA 4415 airfoil and the control of separation using periodic surface motion. Actuation is implemented by bonding two Macro Fiber Composite patches to the underside of the suction surface. Time-resolved measurements reveal that the peak-to-peak displacement of the surface motion is a function of both the amplitude and frequency of the input voltage signal but the addition of aerodynamic forces does not cause significant changes in the surface behavior. The vibration mode is uniform in the spanwise direction for frequencies below 80 Hz; above this frequency, a secondary vibration mode is observed. The flow around the unactuated airfoil exhibits a large recirculation region as a result of laminar separation without reattachment and consequently produces relatively high drag and low lift forces. Various actuation frequencies were examined. When actuated at V f + = 2 . 0 , the spectra in the vicinity of the trailing edge and near-wake were found to be dominated by the actuation frequency. Sharp peaks appear in the spectra suggesting the production of Large Coherent Structures at this frequency. The increased momentum entrainment associated with these enabled a significant suppression of the separated region. The result was a simultaneous increase in C L and decrease in C D and therefore a large increase in the L ∕ D ratio. In addition, a delay in the onset of stall results in a significant increase in the maximum achievable lift.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.11.008
      Issue No: Vol. 76 (2017)
  • Experimental characterisation of the self-excited vibrations of
           spring-loaded valves
    • Authors: Salim El Bouzidi; Marwan Hassan; Samir Ziada
      Pages: 558 - 572
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Salim El Bouzidi, Marwan Hassan, Samir Ziada
      Valves are omnipresent in industrial processes. As a result, they must perform reliably according to their specifications. Spring-loaded valves are particularly susceptible to vibrations, as they are inherently flexible, often operate at small openings, and therefore they are more likely to interact with the surrounding flow. The current study experimentally investigates the self-excitation mechanism of a model spring-loaded valve with an emphasis on the interaction between the system flow and sound fields, and the valve structure. Tests are performed for various values of valve stiffness and maximum allowable valve lift. In each case, the pressure drop across the valve is increased gradually until the valve becomes fully open. The valve was found to oscillate at the fully coupled resonance frequency resulting from the interaction of the valve vibration with the acoustic field of the piping system. The oscillation amplitude was found to be positively correlated to both the pipe length and spring stiffness value. Furthermore, initial spring compression was found to have only moderate effects on the range of static pressures that would cause instability.

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.11.007
      Issue No: Vol. 76 (2017)
  • A mechanism of thrust enhancement on a heaving plate due to flexibility at
           moderately low Reynolds numbers
    • Authors: Yung-Sheng Lin; Yau-Ting Tzeng; Cheng-Ta Hsieh; Chien C. Chang; Chin-Chou Chu
      Pages: 573 - 591
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Yung-Sheng Lin, Yau-Ting Tzeng, Cheng-Ta Hsieh, Chien C. Chang, Chin-Chou Chu
      A numerical study is conducted to investigate the force mechanisms for a 3D heaving flexible plate from the perspective of a diagnostic force element analysis. The problem is relevant to a flapping fish-tail simplified as a flat plate with the leading edge held heaving in the space. The flow is assumed to be laminar with the Reynolds numbers fixed at R e = 200 or 500, and the Strouhal number St ranging from 0.1 to 0.6, and the flexure amplitude of the plate a 0 from 0.1 to 0.25 (dimensionless). As the finite plate is set into unsteady motion, complicated vortex patterns around the plate are generated. It is shown that heaving, whilst increasing thrust generation, also reduces the frictional drag, yet the flexibility promotes thrust generation at the expense of accruing more frictional drag. In the literature, the force (thrust) exerted on the tail-mimicking plate is largely credited to the vortices (vorticity) in the wake. However, this study performs a regional force analysis to show that the vorticity in the wake region supplies approximately 20–30% of the total thrust, especially in the cases of strong thrust generation. Comparable contributions come also from the regions direct above and below the heaving plate (mainly including the attached vortices) as well as from the two side regions (mainly including the tip vortices) next to the flexible plate. In addition, the potential motion associated with the unsteady flapping and the contribution from the surface vorticity are non-negligible constituent force components. The relative importance of the various force contributions was analyzed in detail, and the results may shed light on how a flapping tail generates propulsive efficiency above the critical Strouhal number S t = 0 . 2 .

      PubDate: 2017-12-26T23:38:13Z
      DOI: 10.1016/j.jfluidstructs.2017.11.006
      Issue No: Vol. 76 (2017)
  • Rapid manoeuvring with spanwise-flexible wings
    • Authors: Jaime G. Wong; David E. Rival
      Pages: 1 - 8
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Jaime G. Wong, David E. Rival
      In this study, it is hypothesized that spanwise-profile bending contributes towards limiting leading-edge vortex (LEV) growth and increasing LEV stability in natural swimming and flight, due to the spanwise flow produced by profile bending. Specifically, as a propulsor undulates and subsequently bends, the profile tip can have a phase lag relative to the root, producing both a spanwise flow and an angle-of-attack gradient, transporting vorticity and thus circulation along its span. This relative phase of the profile tip versus the root is investigated experimentally using a combined pitching-and-flapping motion on a nominally two-dimensional NACA0012 profile, utilizing direct measurements of vorticity transport to estimate the circulation budget. In order to measure vorticity transport the entire velocity gradient tensor must be resolved, and therefore 4D-PTV, a high-density, time-resolved volumetric technique, was used to measure the flow around the profile. Tip-leading kinematics were found to increase LEV size and strength due to an unbalanced circulation budget: vorticity was not transported along the span, but instead accumulated to increase circulation. Meanwhile for tip-lagging kinematics, that mimics the bending found in nature, both reduced LEV size and circulation were observed, as vorticity transport acted to balance the circulation budget instead.

      PubDate: 2017-09-08T10:36:06Z
      DOI: 10.1016/j.jfluidstructs.2017.08.006
      Issue No: Vol. 75 (2017)
  • Physical mechanism of intermittency route to aeroelastic flutter
    • Authors: J. Venkatramani; S. Krishna Kumar; Sunetra Sarkar; Sayan Gupta
      Pages: 9 - 26
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): J. Venkatramani, S. Krishna Kumar, Sunetra Sarkar, Sayan Gupta
      Intermittency has been observed in the response of aeroelastic systems in the presence of flow fluctuations. This study focuses on developing an understanding of the physical mechanisms that lead to intermittency in such systems. Specifically, the role of time scales of the input flow fluctuations is investigated. Numerical investigations reveal that flow fluctuations with predominantly long time scales in the pre-flutter regime lead to “on–off” type intermittency. On the other hand, rapid fluctuations constituting of small time scales lead to another qualitatively different intermittency, which is referred to in this paper as “burst” type intermittency. It is further shown that the unsteady wake effects play a crucial role in the burst type intermittency. Measures derived from time series analysis of the aeroelastic response are proposed to identify the different dynamical states quantitatively.

      PubDate: 2017-09-08T10:36:06Z
      DOI: 10.1016/j.jfluidstructs.2017.08.003
      Issue No: Vol. 75 (2017)
  • Interaction dynamics of upstream vortex with vibrating tandem circular
           cylinder at subcritical Reynolds number
    • Authors: R.C. Mysa; Y.Z. Law; R.K. Jaiman
      Pages: 27 - 44
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): R.C. Mysa, Y.Z. Law, R.K. Jaiman
      This numerical study investigates the local unsteady characteristics of transverse wake-induced vibration (WIV) of an elastically mounted downstream circular cylinder in a tandem arrangement at subcritical Reynolds number regime of 5000 ≤ R e ≤ 10000 . The upstream cylinder with an equal diameter is kept fixed and the downstream one is free to vibrate in a direction perpendicular to the freestream flow with a low mass damping parameter m ∗ ζ = 0 . 018 , where m ∗ is mass ratio and ζ is damping. Similar to the recent experiment study, we consider a longitudinal separation L x ∕ D = 4 . 0 in the co-shedding regime, where L x denotes the center-to-center distance and D is the diameter of cylinder. In the present study, we perform three-dimensional simulations to further shed light on the sustained low frequency motion and the larger amplitude of downstream cylinder interacting with a turbulent vortical wake. We employ a nonlinear partitioned iterative scheme and a dynamic subgrid-scale model based on variational formulation for simulating the fluid–structure interaction in a turbulent wake. We assess the transverse amplitude and the frequency response against the experimental measurements for the reduced velocity U r ∈ [ 4 , 14 ] , whereby the reduced velocity is adjusted by changing the freestream Reynolds number. Of particular interest is to study the interaction of freely vibrating downstream cylinder with upstream vortices and the role of stagnation point movement in the transverse load generation over the downstream cylinder. We examine instantaneous energy transfer from the fluid flow to the vibrating downstream cylinder with respect to the movement of stagnation point and the vortex–structure interaction. We compare the WIV response of downstream cylinder against the isolated cylinder with prescribed periodic motion in a freestream flow. Through the vorticity contours and pressure distribution, we finally investigate the upstream vortex interaction with the vibrating downstream cylinder during the oscillation cycle of wake excitation.

      PubDate: 2017-09-08T10:36:06Z
      DOI: 10.1016/j.jfluidstructs.2017.08.001
      Issue No: Vol. 75 (2017)
  • Effect of fluid-thermal–structural interactions on the topology
           optimization of a hypersonic transport aircraft wing
    • Authors: David J. Munk; Dries Verstraete; Gareth A. Vio
      Pages: 45 - 76
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): David J. Munk, Dries Verstraete, Gareth A. Vio
      Aerothermoelasticity plays a vital role in the design of hypersonic aircraft as the coupling between the thermodynamics, aerodynamics and structural dynamics cannot be ignored. While topology optimization has been used in the design of aircraft components, thus far, existing optimization algorithms lack the capability to include aerothermodynamic coupling effects. This article presents an original evolutionary structural topology optimization algorithm that includes hypersonic aerothermoelastic effects. The time-varying temperature distribution is applied through a conjugate heat transfer analysis integrated in time by an unsteady conduction solver, and is coupled to the aerodynamics, which is calculated by a supersonic vortex lattice method. This article analyses the effect of fluid-thermal–structural interactions on the optimization of a hypersonic transport aircraft wing, by optimizing the wing structure with various degrees of coupling. The coupling of the aerothermodynamics drives the optimization of the structural design and therefore must be considered for hypersonic applications. This new optimization algorithm allows the coupling of the aerothermodynamics to be considered in the early stages of the design, potentially avoiding a costly re-design.

      PubDate: 2017-09-08T10:36:06Z
      DOI: 10.1016/j.jfluidstructs.2017.08.007
      Issue No: Vol. 75 (2017)
  • Experimental study on the flutter-induced motion of two-degree-of-freedom
    • Authors: Luca Pigolotti; Claudio Mannini; Gianni Bartoli
      Pages: 77 - 98
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Luca Pigolotti, Claudio Mannini, Gianni Bartoli
      This work investigates the flow-induced motion originating from the classical-flutter instability, and it is motivated by energy-harvesting applications. The influence of several sets of dynamic parameters is studied, improving the scientific understanding of the large-amplitude response and guiding the design of more unstable configurations. Wind-tunnel tests were conducted on elastically-suspended rigid models with an elongated rectangular cross section, undergoing a two-degree-of-freedom motion with transverse (heaving) and rotational (pitching) components. The aeroelastic setup was specifically developed to allow for a large-amplitude motion (about one chord in heaving and more than 90°in pitching) and to simulate an energy-conversion apparatus by increasing the heaving damping (up to about 18% of the critical one) through eddy-current dampers. After a sub-critical bifurcation, large limit-cycle oscillations were recorded, with steady-state amplitudes increasing with the flow speed. For some configurations, a low-amplitude response was also observed around the instability threshold. It was found that a small mass unbalance aft of the elastic axis significantly fosters the system instability and affects the heaving and pitching motion amplitudes. The latter are also markedly influenced by the still-air frequency ratio. In the presence of high values of the heaving damping, the post-critical amplitude is usually reduced, although a destabilising effect of damping was observed in some specific cases. Finally, the motion is magnified for lower-inertia systems.

      PubDate: 2017-09-08T10:36:06Z
      DOI: 10.1016/j.jfluidstructs.2017.07.014
      Issue No: Vol. 75 (2017)
  • Numerical modeling of water hammer with fluid–structure interaction in a
           pipeline with viscoelastic supports
    • Authors: Henclik
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Sławomir Henclik
      In the paper a numerical approach to the four equation model of water hammer (WH) with fluid–structure interaction (FSI) is presented. An algorithm for numerical solution of that model in time domain based on the method of characteristics (MOC) is proposed. Special attention is paid to modeling of the influence of viscoelastic pipe supports. The boundary condition at the support is formulated as a differential equation of junction motion which is solved numerically concurrently with the MOC compatibility equations. Numerical simulations were done with the use of an own computer program. The tests were conducted for a model of real pipeline built in the lab and fastened with specific, complex, supporting system. The numerical results were compared to the experimental records and after some modeling and calibration quite a good agreement was achieved. Basic behaviors in the pressure records were identified and existed discrepancies were discussed and explained. The other physical model tested and preliminary analyzed in the paper is a straight pipeline fixed to the floor only with viscoelastic supports. Such a design created the possibility of significant displacements of the pipeline on the supports and thus allowing for effective testing of the influence of supports stiffness and damping properties on the WH behaviors. The specific initial conditions for that case were formulated, solved and implemented in a computer code. It was found that proper selection of support parameters may produce significant reduction of WH pressure amplitudes, mainly due to effective energy absorption and dissipation at the supports.

      PubDate: 2017-12-12T07:02:52Z
  • Structural analysis of a submerged cylindrical shell subjected to two
           consecutive spherical shock waves
    • Authors: Iakovlev
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): S. Iakovlev
      Three-dimensional structural dynamics of a circular cylindrical shell submerged in fluid and subjected to two consecutive spherical shock waves is addressed using a semi-analytical model based on the classical apparatus of mathematical physics. It is established that for certain values of the delay between the first and second incident wavefronts, the highest stress observed in the system significantly (by up to 50%) exceeds the peak stress observed for the single-front loading of the same intensity. Although this result is quantitatively the same as the one reported for the simplified two-dimensional model of the system, it is demonstrated that there exist very substantial differences between the evolution of the peak stress predicted by the two models when the three-dimensionality of the incident shock waves is pronounced. It is thus established that the presented three-dimensional model is a far more reliable pre-design analysis tool for such loadings than its two-dimensional counterpart.

      PubDate: 2017-12-12T07:02:52Z
  • Mitigation of flutter vibration using embedded shape memory alloys
    • Authors: Nicholas G. Garafolo; Garrett R. McHugh
      Abstract: Publication date: Available online 23 November 2017
      Source:Journal of Fluids and Structures
      Author(s): Nicholas G. Garafolo, Garrett R. McHugh
      Aeroelastic flutter is a major concern for designers of planes, boats, turbines and other systems that experience aerodynamic loading. The typically undesirable phenomenon can cause aircraft instability, high cycle fatigue, excess noise, and in some cases catastrophic failure. This research aims to quantify the effect of embedded shape memory alloys (SMA) as an active suppression system to mitigate vibrations induced by aeroelastic flutter through an experimental investigation. A silicone plate with embedded SMA wire was designed. A subsonic wind tunnel was utilized to actuate flutter vibration. Control samples were created using the same dimensions and silicone material. One control sample contained embedded aluminum wire while the other sample contained no embedded material. Frequencies at the tip of the fluttering plates were calculated using a Fast Fourier Transfer (FFT) at varying temperatures. Experiments resulted in an average natural frequency shift of 44.6% at the sample tip upon actuation of the SMA material. Two dimensional vibrational scanning tests revealed three vibration modes in the fluttering flags. A first bending mode revealed a tip amplitude decrease of 34.4% upon actuation of the embedded SMA material. A second bending mode revealed a tip amplitude decrease of 33.6%. A torsional mode revealed a tip amplitude decrease of 60.7%. The frequency of the embedded aluminum wire sample remained relatively constant at low and high temperatures, leading to the conclusion that the frequency shift of the SMA sample was a result of the shape memory effect.

      PubDate: 2017-12-12T07:02:52Z
      DOI: 10.1016/j.jfluidstructs.2017.09.013
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