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  Subjects -> ENGINEERING (Total: 2282 journals)
    - CHEMICAL ENGINEERING (192 journals)
    - CIVIL ENGINEERING (186 journals)
    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1204 journals)
    - ENGINEERING MECHANICS AND MATERIALS (385 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (68 journals)
    - MECHANICAL ENGINEERING (90 journals)

CIVIL ENGINEERING (186 journals)                     

Showing 1 - 186 of 186 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: 34)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 27)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 30)
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: 1)
ATBU Journal of Environmental Technology     Open Access   (Followers: 3)
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: 9)
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)
Berkeley Planning Journal     Open Access   (Followers: 7)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 15)
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: 11)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 10)
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: 5)
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: 17)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 9)
Civil Engineering Dimension     Open Access   (Followers: 8)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 258)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 10)
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: 8)
Construction Management and Economics     Hybrid Journal   (Followers: 21)
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: 16)
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: 8)
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: 6)
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
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: 13)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 8)
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: 4)
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: 6)
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: 11)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 7)
Journal of Civil Engineering Research     Open Access   (Followers: 6)
Journal of Civil Society     Hybrid Journal   (Followers: 3)
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 Construction Engineering, Technology & Management     Full-text available via subscription   (Followers: 4)
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: 12)
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: 4)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 10)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 11)
Journal of Offshore Structure and Technology     Full-text available via subscription  
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: 39)
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 South African Institution of Civil Engineering     Open Access   (Followers: 4)
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil dan Perencanaan     Open Access  
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)
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 6)
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: 7)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 11)
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)
Recent Trends In Civil Engineering & Technology     Full-text available via subscription   (Followers: 4)
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: 9)
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: 4)
Steel Construction - Design and Research     Hybrid Journal   (Followers: 3)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 9)
Structural Concrete     Hybrid Journal   (Followers: 11)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 9)
Structural Engineering International     Full-text available via subscription   (Followers: 11)
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: 12)
Structures     Hybrid Journal   (Followers: 1)
Study of Civil Engineering and Architecture     Open Access   (Followers: 8)
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  [3044 journals]
  • Suppression of the vortex-induced vibration of a circular cylinder
           surrounded by eight rotating wake-control cylinders
    • Authors: M. Silva-Ortega; G.R.S. Assi
      Pages: 354 - 362
      Abstract: Publication date: Available online 20 July 2017
      Source:Journal of Fluids and Structures
      Author(s): M. Silva-Ortega, G.R.S. Assi
      The present work investigates the use of a polar array of 8 wake-control cylinders as a means of suppressing the vortex-induced vibration (VIV) of a larger circular cylinder. The diameter of the control cylinders and their rotation speed were the main parameters investigated. Experiments have been performed in water at Reynolds numbers between 5000 and 50,000. The rotating cylinders suppressed the peak amplitude of displacement by around 70% when compared to that of a bare cylinder. A similar response was obtained even if the rotation speed of the control cylinders was kept constant in relation to the flow speed. A specific configuration with 8 non-rotating control cylinders achieved an even better 99% suppression. As a consequence of reduced vibrations, the fluctuation of lift and mean drag were not as amplified due to VIV. The results pave the way for further studies concerning system optimization and support the development of efficient VIV suppressors and dynamic positioning systems for large floating offshore platforms and other applications.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.expthermflusci.2017.03.020
      Issue No: Vol. 85 (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
           plates
    • 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)
       
  • Investigations of offshore breaking wave impacts on a large offshore
           structure
    • Authors: Zheng Zheng Hu; Tri Mai; Deborah Greaves; Alison Raby
      Pages: 99 - 116
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Zheng Zheng Hu, Tri Mai, Deborah Greaves, Alison Raby
      This paper describes numerical and laboratory investigations that have been carried out to gain a better understanding of the physical processes involved in offshore breaking wave impacts on a large offshore structure. The findings are relevant to offshore and coastal structures and to identifying the extreme loads, peak pressures and maximum run-up needed for their design. A truncated wall in a wave flume is used to represent a vertical section of an FPSO (Floating Production Storage and Offloading) hull, which is a typical large offshore structure. Four types of wave impact were identified in the tests, and are referred to as slightly-breaking, flip-through, large air pocket and broken wave impacts. Physical modelling was undertaken in Plymouth University’s COAST Laboratory and the open source Computational Fluid Dynamics (CFD) package-Open Field Operation and Manipulation (OpenFOAM) was adopted to study focused wave generation and wave impact on the hull. The method solves incompressible Unsteady Reynolds-averaged Navier–Stokes Equations (URANSE) using a finite volume method with two phase flows. A Volume of Fluid (VoF) interface capturing approach is used to model the free surface. A NewWave boundary condition is used to generate focused wave groups based on the first plus second-order (hereafter second-order) Stokes wave theory in the Numerical Wave Tank (NWT). By changing the focus location with respect to the wall, the wave impact type was altered in both the numerical and laboratory investigations. The results show that for the four wave impact types tested good agreement was achieved between numerical predictions and experimental measurements of surface elevation, run up and impact force. The peak pressures predicted by the simulation are lower than the experimentally measured results due to time step constraints, although the shape of the pressure time history is very similar. Four distinct wave impact types are identified for the vertical hull section and are found to be similar in character to those observed for a full depth vertical wall. The predicted force on the hull is found to be greatest for the large air pocket impact, and the highest run-up for the slightly-breaking wave impact. The pressure records show a high degree of spatial and temporal variation though the highest pressure recorded at any location was due to flip-through. This research has shown that different characteristic wave impact types are responsible for maximum load and greatest wave run-up and so need to be considered separately for design purposes.

      PubDate: 2017-09-14T07:37:12Z
      DOI: 10.1016/j.jfluidstructs.2017.08.005
      Issue No: Vol. 75 (2017)
       
  • On limit cycle oscillations of typical aeroelastic section with different
           preset angles of incidence at low airspeeds
    • Authors: Carlos R. dos Santos; Daniel A. Pereira; Flávio D. Marques
      Pages: 19 - 34
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Carlos R. dos Santos, Daniel A. Pereira, Flávio D. Marques
      Helicopter blades and wind turbines are examples of aeroelastic systems that can reach high angles of attack and can vibrate due to the effects of the dynamic stall, thereby leading to fatigue problems or performance loss. Structural and aerodynamic nonlinearities influence the aforementioned behavior and their modeling is crucial for phenomena characterization. Such system modeling requires proper knowledge of the physical events during the stall, which can be better achieved by validating the model with experimental data. This work investigates the nonlinear dynamics of a NACA 0012 airfoil under the influence of structural and aerodynamic nonlinearities due to dynamic stall effects at high angles of attack. Experimental and numerical analyses are carried out. Moreover, different preset incidence angles for the typical aeroelastic section are also considered. The aeroelastic signals are used for estimating the Hopf bifurcation onset and to build the bifurcation diagrams. By using a typical section model with two degrees of freedom coupled to the Beddoes–Leishman aerodynamic model, numerical results have been able to capture with good precision experimental features. The onset of the Hopf bifurcations allows the determination of the flutter critical airspeed. Results for zero preset angle show that limit cycle oscillations from small to moderate displacements are mostly driven by the hardening nonlinearity. After reaching larger angles of incidence the dynamic stall nonlinearities supplant those from structural sources. For higher preset angles, the dynamic stall effects tend to increase the energy associated with pitching motion and to reduce amplitudes in plunge motion. Another effect related to the aerodynamic nonlinearities relies on the increase of the flutter velocity by around 10% for preset angles ranging from zero up to ten degrees. For higher preset angles an abrupt reduction in the flutter onset velocity is observed.

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.07.008
      Issue No: Vol. 74 (2017)
       
  • Nonlinear oscillations of shape-morphing submerged structures: Control of
           hydrodynamic forces and power dissipation via active flexibility
    • Authors: Syed N. Ahsan; Matteo Aureli
      Pages: 35 - 52
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Syed N. Ahsan, Matteo Aureli
      In this paper, we consider nonlinear oscillations of a shape-morphing plate submerged in a quiescent, Newtonian, viscous fluid. We investigate the two-dimensional problem arising from two prescribed concurrent periodic motions of the plate: a rigid oscillation along its transverse direction coupled to a shape-morphing deformation to an arc of a circle with prescribed maximum curvature. As opposed to existing literature concerned with passive flexible structures, this study focuses on actively prescribed deformations of the structure as a means to manipulate the vortex-shedding and convection patterns responsible for hydrodynamic forces and power dissipation during underwater oscillations. We elucidate the potential of the proposed shape-morphing strategy in regulating the added mass and damping effects along with the hydrodynamic power dissipation both in the linear and nonlinear hydrodynamic regime, by utilizing a linear boundary integral formulation as well as computational fluid dynamics simulations. Results show the possibility of minimizing the hydrodynamic power dissipation for optimal values of the imposed curvature, along with significant reduction of the hydrodynamic forces. A simplified semianalytical argument relates these novel effects to specific geometric properties of the plate motion. Findings from this study are directly relevant to cantilever-based sensing and actuation systems operating in fluids, where control and modulation of oscillation quality factors, hydrodynamic forces, and power losses is beneficial.

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.06.010
      Issue No: Vol. 74 (2017)
       
  • Experimental sensitivity of vortex-induced vibrations to localized wake
           perturbations
    • Authors: J.I. Jiménez-González; F.J. Huera-Huarte
      Pages: 53 - 63
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): J.I. Jiménez-González, F.J. Huera-Huarte
      We present the experimental sensitivity of vortex-induced vibration (VIV) to localized perturbations, in the wake of a low mass-damping one-degree-of-freedom circular cylinder subject to uniform cross-flow. Regions of VIV sensitivity have been identified, clearly indicating positions in the wake where control systems should be placed in order to attenuate VIV amplitudes. As a validation of the sensitivity maps, we demonstrate how by using control cylinders with diameters of only 12% of the main cylinder diameter, reductions of VIV response of more than 65%, can be reached. The use of Digital Particle Image Velocimetry (DPIV) has allowed us to identify the physical mechanisms underlying the VIV response modifications induced by the control cylinders.

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.07.010
      Issue No: Vol. 74 (2017)
       
  • Updated VOFIRE algorithm for fast fluid–structure transient dynamics
           with multi-component stiffened gas flows implementing anti-dissipation on
           unstructured grids
    • Authors: Vincent Faucher; Michal Bulik; Pascal Galon
      Pages: 64 - 89
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Vincent Faucher, Michal Bulik, Pascal Galon
      The present paper is dedicated to the simulation of fast transient phenomena involving multi-component flows with fluid–structure interaction and ALE grid motion, where the fluid interfaces are tracked using the VOFIRE anti-dissipative scheme for unstructured meshes. It introduces an extension of the existing scheme in EUROPLEXUS software, written for liquid–gas flows only, to handle a combination of stiffened gases as equations of state for the fluid components, thus increasing its genericity and overcoming some limitations, at the cost of significantly modifying its implementation. The proposed methodology is proven to achieve its goals through validation examples with fluid only, such as the sloshing of a liquid in a decelerated tank or a gas–gas interaction with Richtmyer–Meshkov instability. Two large scale three-dimensional examples with full fluid–structure interaction are then provided to fully demonstrate the capabilities and the robustness of the complete proposed computational framework.

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.07.001
      Issue No: Vol. 74 (2017)
       
  • Predicting modal characteristics of a cluster of cylinders in axial flow:
           From potential flow solutions to coupled CFD–CSM calculations
    • Authors: Jeroen De Ridder; Joris Degroote; Katrien Van Tichelen; Jan Vierendeels
      Pages: 90 - 110
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Jeroen De Ridder, Joris Degroote, Katrien Van Tichelen, Jan Vierendeels
      External fluid flow has a number of effects on the dynamics of a submersed structure: e.g., a solitary cylinder exposed to an external flow experiences added mass and damping due to the presence of the surrounding fluid. At high axial flow velocities relative to the stiffness of the cylinder, coupled instabilities such as flutter and divergence occur. Compared to a solitary cylinder, a cluster of cylinders also experiences inter-cylinder coupling: pressure perturbations in the fluid due to the movement or acceleration of one cylinder force another cylinder to move. Consequently, the different cylinders can move in organized patterns. In this contribution, modal characteristics of a 7-rod bundle will be predicted by linear theory as well as by coupled CFD–CSM (Computational Fluid Dynamics — Computational Structure Mechanics) calculations. In the first part, fluid forces which lead to coupling of motion are computed with classical potential flow theory and URANS (Unsteady Reynolds-Averaged Navier–Stokes). Those forces are divided in a contribution in phase with the acceleration and a contribution in phase with the velocity of a cylinder. In the second part, modal characteristics of a 7 cylinder bundle are computed with coupled CFD–CSM simulations. The initial perturbations, which are required for the time-domain simulations come from a simplified structural model, with potential flow coupling between cylinders. The results are compared to linear theory. In the final part, approximations are proposed to predict upper and lower bounds of eigenfrequencies and damping, using calculations with only one cylinder.

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.07.006
      Issue No: Vol. 74 (2017)
       
  • Piezoaeroelastic energy harvesting based on an airfoil with double plunge
           degrees of freedom: Modeling and numerical analysis
    • Authors: Yining Wu; Daochun Li; Jinwu Xiang; Andrea Da Ronch
      Pages: 111 - 129
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Yining Wu, Daochun Li, Jinwu Xiang, Andrea Da Ronch
      In this paper, a piezoaeroelastic energy harvester based on an airfoil with double plunge degrees of freedom is proposed to additionally take advantage of the vibrational energy of the airfoil pitch motion. The analytical model of the proposed harvester is built, and an equivalent model using the well-explored pitch–plunge configuration is presented. The nonlinear aerodynamics is calculated based on the dynamic stall model. The dynamic response, average power output, energy harvesting efficiency, and cut-in speed (flutter speed) of the proposed harvester are numerically studied. It is demonstrated that the harvester with double-plunge configuration outperforms its equivalent pitch–plunge counterpart in terms of both the power output and energy harvesting efficiency beyond the flutter boundary. In addition, case studies are performed to reduce the cut-in speed and to enhance the energy harvesting efficiency of the proposed harvester, including the airfoil mass characteristics, the configuration, mass, damping, and stiffness characteristics of the two plunge supporting devices, and the load resistances in the external circuits. It is shown that the cut-in speed is greatly reduced by increasing the airfoil mass while tuning the mass eccentricity. The mass of the first (windward) supporting device should be a bit smaller than that of the second one for an applicable cut-in speed and a high-energy harvesting efficiency. Besides, the decrease of airfoil mass moment of inertia or the damping of the supporting devices is shown to be beneficial for the energy harvesting performance. In addition, the optimal location of the first supporting device is found to be at the airfoil leading edge. Decreasing the distance between the two supporting devices reduces the cut-in speed. The load resistances affect the cut-in speed slightly, and optimal values are found to maximize the energy harvesting efficiency.

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.06.009
      Issue No: Vol. 74 (2017)
       
  • Effect of the angle of attack on the transient lift during the interaction
           of a vortex with a flat plate. Potential theory and experimental results
    • Authors: J. Alaminos-Quesada; R. Fernandez-Feria
      Pages: 130 - 141
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): J. Alaminos-Quesada, R. Fernandez-Feria
      The dynamics of a two-dimensional vortex interacting with a flat plate at different angles of attack α is analysed using potential flow theory based on conformal mapping varying the nondimensional separation distance h ∕ c of the upstream incoming vortex to the plate ( c is the chord length of the plate) and the vortex intensity Γ l . Transient lift forces measured in a wind tunnel are also compared with the potential theory results for a given Γ l and several values of h ∕ c and α . For the Reynolds number considered in the experiments (about 25 000) it is found that the potential theory predicts reasonably well the transient fluctuation in the lift force provided that the separation distance is not too close to the critical one h ∗ ∕ c at which the vortex trajectory given by the potential theory bifurcates. We find that the separation distance generating the highest induced lift is around this critical value h ∗ ∕ c , which, according to the potential theory, is displaced about − 2 . 3 ( 1 − 0 . 07 Γ l 1 ∕ 2 ) α in relation to the zero angle of attack for the same Γ l . Potential theory also predicts that the maximum peak of the lift fluctuation depends on α only through the relative separation h − h ∗ ∕ c , and that the maximum lift is substantially larger when a clockwise vortex passes below the plate than when it passes above the plate, for the same vortex intensity Γ l and relative separation distance. The opposite happens for a counter-clockwise vortex. This asymmetry in the maximum lift fluctuation increases slightly with Γ l , approaching a ratio of almost two for large Γ l .

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.07.013
      Issue No: Vol. 74 (2017)
       
  • URANS predictions of wave induced loads and motions on ships in regular
           head and oblique waves at zero forward speed
    • Authors: Yuting Jin; Shuhong Chai; Jonathan Duffy; Christopher Chin; Neil Bose
      Pages: 178 - 204
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Yuting Jin, Shuhong Chai, Jonathan Duffy, Christopher Chin, Neil Bose
      The paper presents predictions on the hydrodynamics of a conceptual floating liquefied natural gas (FLNG) and a liquefied natural gas (LNG) carrier in regular head and oblique sea waves using an unsteady Reynolds-Averaged Navier–Stokes (URANS) solver. Initially, a verification and validation study is performed on estimating the numerical uncertainties in the presented URANS simulations. Using the verified numerical setup, ship hydrodynamic properties including wave induced loads as well as ship motion responses are investigated for different wave conditions. The computed time history results are decomposed by Fourier Series to estimate the wave load and ship motion transfer functions. These results show good correlation with predictions from model tests and potential flow calculations. From the computations, it is observed when increasing the wave length, wave diffraction around the ship becomes less profound and the water depth starts to influence the transfer functions. Full scale computations in head and oblique sea waves are also presented and compared with model scale predictions for investigating possible scale effects. The differences are found to be close to the numerical uncertainties, indicating minor influences of scale effects on the prediction of wave loads and ship motion responses for the tested cases.

      PubDate: 2017-09-02T10:14:38Z
      DOI: 10.1016/j.jfluidstructs.2017.07.009
      Issue No: Vol. 74 (2017)
       
  • Modulation of aerodynamic force on a 2D elliptic body via passive splitter
           pitching under high turbulence
    • Authors: Yaqing Jin; Imran Hayat; Leonardo P. Chamorro
      Pages: 205 - 213
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Yaqing Jin, Imran Hayat, Leonardo P. Chamorro
      The mean and fluctuating aerodynamic force on an elliptic body of infinite aspect ratio with hinged splitters were experimentally studied under high incoming turbulence for various angle of attack A o A of the body, Reynolds numbers and splitter length. High-resolution load cell was used to measure the mean and unsteady lift and drag forces of the body; whereas a hotwire anemometry was employed to characterize the incoming turbulence and get insight on the wake flow. Results show that the attached splitters reduce the lift and drag coefficients for A o A well beyond stall. Interestingly, the splitter length did not play a noticeable role on the mean aerodynamic force; this parameter just induced minor effects on the fluctuation counterpart. Such phenomenon appear to be inherently related to the background turbulence levels. Compared to the bare body, the force coefficients exhibit stronger dependence on Reynolds number due to the dynamics induced by the splitter pitching. In general, the force fluctuations are dominated by the natural frequency of the setup under the high turbulence. The joint distribution of the instantaneous lift and drag forces reveals that under sufficiently high A o A , the vortex shedding dominates the force fluctuations along the major axis of the body; whereas the splitters can efficiently dampen the vortex shedding and mitigate the overall force fluctuations.

      PubDate: 2017-09-02T10:14:38Z
      DOI: 10.1016/j.jfluidstructs.2017.08.004
      Issue No: Vol. 74 (2017)
       
  • Experiments on the aerodynamic behaviour of square cylinders with rounded
           corners at Reynolds numbers up to 12 million
    • Authors: Nils Paul van Hinsberg; Günter Schewe; Markus Jacobs
      Pages: 214 - 233
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Nils Paul van Hinsberg, Günter Schewe, Markus Jacobs
      The influence of the angle of incidence and corner radius on the aerodynamics of square-section cylinders is studied by means of wind tunnel experiments. Two different corner radii ( r ∕ D = 0 . 16 and 0.29) were investigated at three angles of incidence ( α = 0 ° , − 22 . 5 ° and − 45 ° ). Steady and unsteady global forces and local surface pressures were measured in the high-pressure wind tunnel in Göttingen. The Reynolds number was varied up to values as high as 12 × 106, thereby spanning the known flow state regimes up to high transcritical. The results demonstrated that a decrease of the cylinder’s bluffness induced lower maximum drag coefficients and r.m.s. values, as well as higher Strouhal numbers in all flow state regimes. Furthermore, the critical Reynolds numbers shifted to significantly lower values. For the cylinder configurations at α = 0 ° no upper transition or transcritical flow state was present up to R e D = 12 million. A decrease in the angle of incidence resulted in a significant reduction of the length of the supercritical flow state, a shift of the drag force, Strouhal number and base pressure to higher values and an increase of the critical Reynolds numbers. The cylinders at non-zero angles of incidence all displayed a clear critical flow state, at which two discontinuous transitions were observed, accompanied by jumps in the C D and C L values and the Strouhal number. Only three out of six studied configurations experienced hysteresis, where for the high corner radius configuration at α = 0 ° a particularly broad hysteresis effect was measured.

      PubDate: 2017-09-02T10:14:38Z
      DOI: 10.1016/j.jfluidstructs.2017.08.002
      Issue No: Vol. 74 (2017)
       
  • Low Reynolds number swimming of helical structures in circular channels
    • Authors: Ebru Demir; Serhat Yesilyurt
      Pages: 234 - 246
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Ebru Demir, Serhat Yesilyurt
      Rotating helical structures are very effective in low Reynolds number swimming and propulsion. Helical rods are extensively studied theoretically and computationally with asymptotical methods, but the effects of the geometric variables in full-scale and the performance of other helical structures, such as ribbons and Archimedean screws, are also important for the understanding of swimming in confinements and design of micro swimming robots. In this study, a CFD model is developed to study swimming of helical rods, ribbons, screws and filaments, in circular channels under constant angular velocity or constant external torque. Effects of geometric parameters and the confinement radius on the swimming velocity and efficiency are demonstrated. Wavelength and amplitude of the helical wave, filament radius, thickness and width of ribbons, and eccentricity of tails are studied. Swimming performance of magnetically coated ribbons is compared with the ribbons with magnetic heads. Theoretical results in literature are used to validate the CFD results and to identify the role of hydrodynamic interactions between helical body and the channel wall.

      PubDate: 2017-09-02T10:14:38Z
      DOI: 10.1016/j.jfluidstructs.2017.07.005
      Issue No: Vol. 74 (2017)
       
  • Viscous damping effect on the aeroelastic stability of subsonic wings:
           Introduction of the U–K method
    • Authors: Farshad Beheshtinia; Rohollah Dehghani Firouz-Abadi; Mohammad Rahmanian
      Pages: 1 - 15
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): Farshad Beheshtinia, Rohollah Dehghani Firouz-Abadi, Mohammad Rahmanian
      This study aims at introduction of a novel method for evaluating the effect of viscous damping on the aeroelastic stability boundaries. The K-method is well-known for being one of the fastest methods in determining the instability conditions (i.e. critical speed and its corresponding frequency). However, formulation of the K-method is developed for aeroelastic systems without viscous damping and solution is valid where the introduced artificial damping is zero. Taking into account the framework of the K-method in general, this study has tried to remove the major shortcoming of the K-method, i.e. investigation of the effect of viscous damping on the aeroelastic stability boundaries. The aeroelastic feasibility of the introduced method is studied via the analysis of typical sections and subsonic high-aspect ratio wings. Parameter studies provided in the present investigation, indicate that viscous damping may alter the stability conditions significantly.

      PubDate: 2017-06-01T13:22:10Z
      DOI: 10.1016/j.jfluidstructs.2017.05.006
      Issue No: Vol. 73 (2017)
       
  • The role of Reynolds number in the fluid-elastic instability of tube
           arrays
    • Authors: A. Ghasemi; N.K.-R. Kevlahan
      Pages: 16 - 36
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): A. Ghasemi, N.K.-R. Kevlahan
      The onset of fluid-elastic instability in tube arrays is thought to depend primarily on the mean flow velocity, the Scruton number and the natural frequencies of the tubes. However, evidence from experiments suggests that the Reynolds number is also an important parameter, although the available data are insufficient to understand or quantify this effect. We use high resolution direct numerical simulations to solve the penalized two-dimensional Navier–Stokes equations in order to accurately model turbulent flow through tube arrays with a pitch to diameter ratio P ∕ D = 1 . 5 . To investigate the Reynolds number effect we perform simulations that independently vary the mean flow velocity and the Reynolds number at fixed Scruton number. Parameters are chosen so that the simulations are well outside the lock-in regime of resonant vortex excitation. Increasing Reynolds number and mean flow velocity both have strong de-stabilizing effects for rotated arrays. For in-line arrays the effect is weaker and not monotonic with increasing Reynolds number and mean flow velocity. This study clarifies how the onset of fluid-elastic instability depends on Reynolds number (and hence turbulence intensity) and reduces uncertainties arising from the experimental data, which usually do not account for the effect of Reynolds number. It also demonstrates the usefulness of two-dimensional direct numerical simulations to investigate fluid-elastic instability at turbulent Reynolds numbers.

      PubDate: 2017-06-15T13:36:02Z
      DOI: 10.1016/j.jfluidstructs.2017.05.004
      Issue No: Vol. 73 (2017)
       
  • Linear sloshing in a 2D rectangular tank with a flexible sidewall
    • Authors: Ida M. Strand; Odd M. Faltinsen
      Pages: 70 - 81
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): Ida M. Strand, Odd M. Faltinsen
      A 2D rectangular sloshing tank with a flexible sidewall have been studied analytically and numerically, with a focus on the coupling between sloshing and the flexible wall. This analysis introduces new knowledge of the effect of internal motions and flow in a membrane structure with a free surface, such as closed flexible fish cages. A framework for analyzing coupled fluid–membrane interaction in the time, and frequency domain in 2D have been developed. The analytical solution gives new knowledge about the effect of the deformations on the linear pressure inside the tank. Coupled eigenfrequencies and the transfer functions for two different membrane lengths due to sway excitation have been found both analytically and numerically. The analytical and numerical results agree. The eigenfrequencies of the system are highly dependent on both the tension and the 2D membrane length. If we consider a given value of tension, then the eigenfrequency of the coupled system is smaller than the sloshing frequency of the rigid tank for any given n . If the tension is small, and we consider a given sloshing frequency of the rigid tank, then there can be more than n eigenfrequencies of the coupled system that is lower than the sloshing frequency of the rigid tank. For large tensions, the eigenfrequencies of the system become the sloshing frequency of a rigid tank. For low tensions, numerical challenges for the direct numerical solution for frequencies close to the natural sloshing frequencies were pointed out.

      PubDate: 2017-06-21T08:52:35Z
      DOI: 10.1016/j.jfluidstructs.2017.06.005
      Issue No: Vol. 73 (2017)
       
  • An efficient fluid–structure interaction model for optimizing
           twistable flapping wings
    • Authors: Q. Wang; J.F.L. Goosen; F. van Keulen
      Pages: 82 - 99
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): Q. Wang, J.F.L. Goosen, F. van Keulen
      Spanwise twist can dominate the deformation of flapping wings and alters the aerodynamic performance and power efficiency of flapping wings by changing the local angle of attack. Traditional Fluid–Structure Interaction (FSI) models, based on Computational Structural Dynamics (CSD) and Computational Fluid Dynamics (CFD), have been used to investigate the influence of twist on the power efficiency. However, it is impractical to use them for twist optimization due to the high computational cost. On the other hand, it is of great interest to study the optimal twist of flapping wings. In this work, we propose a computationally efficient FSI model based on an analytical twist model and a quasi-steady aerodynamic model which replace the expensive CSD and CFD methods. The twist model uses a polynomial to describe the change of the twist angle along the span. The polynomial order is determined based on a convergence study. A nonlinear plate model is used to evaluate the structural response of the twisted wing. The adopted quasi-steady aerodynamic model analytically calculates the aerodynamic loads by including four loading terms which originate from the wing’s translation, rotation, their coupling and the added-mass effect. Based on the proposed FSI model, we optimize the twist of a rectangular wing by minimizing the power consumption during hovering flight. The power efficiency of optimized twistable and rigid wings is studied. Comparisons indicate that the optimized twistable wings exhibit power efficiencies close to the optimized rigid wings, unless the pitching amplitude at the wing root is limited. When the pitching amplitude at the root decreases by increasing the root stiffness, the optimized rigid wings need more power for hovering. However, with the help of wing twist, the power efficiencies of optimized twistable wings with a prescribed root stiffness are comparable with the twistable wings with an optimal root stiffness. This observation provides an explanation for the different levels of twist exhibited by insect wings. The high computational efficiency of the proposed FSI model allows further application to parametric studies and optimization of flapping wings. This will enhance the understanding of insect wing flexibility and help the design of flexible artificial wings for flapping wing micro air vehicles.

      PubDate: 2017-06-21T08:52:35Z
      DOI: 10.1016/j.jfluidstructs.2017.06.006
      Issue No: Vol. 73 (2017)
       
  • Extension of the Non-Linear Harmonic method for the study of the dynamic
           aeroelasticity of horizontal axis wind turbines
    • Authors: Sergio González Horcas; François Debrabandere; Benoît Tartinville; Charles Hirsch; Grégory Coussement
      Pages: 100 - 124
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): Sergio González Horcas, François Debrabandere, Benoît Tartinville, Charles Hirsch, Grégory Coussement
      In this paper an innovative methodology for the study of horizontal axis wind turbines dynamic aeroelasticity is presented. It can be understood as an extension of the Non-Linear Harmonic (NLH) method, an efficient computational approach for the analysis of unsteady periodic flows. A linearized model of the structure consisting of a set of mode shapes and natural frequencies was included. The aeroelastic equilibrium was ensured through a set of equations linking the structural displacements and the fluid loads for both the time-averaged and the harmonic contributions. First, the developed methodology is tested in the framework of a 2D cylinder mounted on a single degree of freedom elastic system and undergoing Vortex Induced Vibrations (VIV). The results are compared with previous experimental and computational studies, revealing the potential of the method for the prediction of both the shedding frequency and the aeroelastic response. Secondly, the dynamic aeroelasticity of the complete DTU 10MW RWT wind turbine (i.e. including the tower) is assessed. A nominal operating point is studied, and the rotor flexibility is considered via a blade structural model. The results of this Fluid–Structure Interaction (FSI) simulation are compared with two additional computations, both assuming rigid blades, that modeled the isolated DTU 10MW RWT rotor and the complete machine. This allowed to distinguish the impact of the blade flexibility on the rotor performance from the potential effects associated to the presence of the tower. In particular, the consideration of the aeroelasticity led to a decrease of the predicted time-averaged rotor loads and the corresponding amplitudes of oscillation. For its application on the DTU 10MW RWT, the developed methodology was found to be one order of magnitude faster than a standard time marching approach.

      PubDate: 2017-06-28T15:36:23Z
      DOI: 10.1016/j.jfluidstructs.2017.06.008
      Issue No: Vol. 73 (2017)
       
  • Aero-hygro-thermal stability analysis of higher-order refined supersonic
           FGM panels with even and uneven porosity distributions
    • Authors: Mohammad Reza Barati; Hossein Shahverdi
      Pages: 125 - 136
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): Mohammad Reza Barati, Hossein Shahverdi
      In this paper, porosity-dependent aero-hygro-thermal instability of functionally graded (FG) panels is investigated by developing a higher-order refined shear deformable theory for the first time. Porosities are randomly distributed around the cross section of FG panel. Hygro-thermo-elastic material properties of porous FG panel are described using a modified power-law function accounting for even and uneven porosity distributions. Based on the presented refined shear deformation theory, it is possible to examine instability regions of thicker FG panels without using a shear correction factor. Employing extended Hamilton’s principle, the governing equations of FG panel under supersonic airflow simulated via first-order piston theory are obtained. It is concluded that porosity volume fraction, type of porosities, hygro-thermal environment, material gradation and slenderness ratio have major roles on the prediction of divergence and flutter boundaries of porous FG panels.

      PubDate: 2017-06-28T15:36:23Z
      DOI: 10.1016/j.jfluidstructs.2017.06.007
      Issue No: Vol. 73 (2017)
       
  • Model-form and predictive uncertainty quantification in linear
           aeroelasticity
    • Authors: C.T. Nitschke; P. Cinnella; D. Lucor; J.-C. Chassaing
      Pages: 137 - 161
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): C.T. Nitschke, P. Cinnella, D. Lucor, J.-C. Chassaing
      In this work, Bayesian techniques are employed to quantify model-form and predictive uncertainty in the linear behavior of an elastically mounted airfoil undergoing pitching and plunging motions. The Bayesian model averaging approach is used to construct an adjusted stochastic model from different model classes for time-harmonic incompressible flows. From a set of deterministic function approximations, we construct different stochastic models, whose uncertain coefficients are calibrated using Bayesian inference with regard to the critical flutter velocity. Results show substantial reductions in the predictive uncertainties of the critical flutter speed compared to non-calibrated stochastic simulations. In particular, it is shown that an efficient adjusted model can be derived by considering a possible bias in the random error term on the posterior predictive distributions of the flutter index.

      PubDate: 2017-06-28T15:36:23Z
      DOI: 10.1016/j.jfluidstructs.2017.05.007
      Issue No: Vol. 73 (2017)
       
  • Three-dimensional numerical simulation of two-degree-of-freedom VIV of a
           circular cylinder with varying natural frequency ratios at Re=500
    • Authors: Enhao Wang; Qing Xiao; Atilla Incecik
      Pages: 162 - 182
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): Enhao Wang, Qing Xiao, Atilla Incecik
      The two-degree-of-freedom (2DOF) vortex-induced vibration (VIV) of a circular cylinder with varying in-line to cross-flow natural frequency ratios ( f ∗ = f n x ∕ f n y ) is studied using a three-dimensional (3D) computational fluid dynamics (CFD) approach. Numerical simulation is carried out for a constant mass ratio of 2 at a fixed Reynolds number Re = 500 . The reduced velocity ranges from 2 to 12. Three natural frequency ratios are considered, i.e., f ∗ = 1 , 1 . 5 and 2. The structural damping is set to zero to maximise the response of the cylinder. The main objective of this study is to investigate the effect of f ∗ on the 2DOF VIV responses and the 3D characteristics of the flow. It is discovered that there is a significant increase in the vibration amplitude, and the peak amplitude shifts to a higher reduced velocity when f ∗ increases from 1 to 2. A single-peak cross-flow response is observed for the identical in-line and cross-flow mass ratios when f ∗ = 2 . Dual resonance is found to exist over the range of f ∗ studied. The preferable trajectories of the cylinder in the lock-in range are counterclockwise figure-eight orbits. Oblique figure-eight trajectories appear at V r = 6 , 7 and 8 when f ∗ = 1 . The third harmonic component which is observed in the lift fluctuation increases with f ∗ . The correlation decreases in the lock-in range and reaches its minimum value around the transition region between the lock-in and post-lock-in ranges. Three vortex shedding modes (2S, P + S and 2P) appear in the present simulation. A dominant P + S mode is associated with the oblique figure-eight trajectories. Variation of vortex shedding flows along the cylinder is observed leading to the poor correlation of the sectional lift forces.

      PubDate: 2017-07-10T06:50:26Z
      DOI: 10.1016/j.jfluidstructs.2017.06.001
      Issue No: Vol. 73 (2017)
       
  • Pseudo three-dimensional simulation of aeroelastic response to turbulent
           wind using Vortex Particle Methods
    • Authors: Khaled Ibrahim Tolba; Guido Morgenthal
      Pages: 1 - 24
      Abstract: Publication date: July 2017
      Source:Journal of Fluids and Structures, Volume 72
      Author(s): Khaled Ibrahim Tolba, Guido Morgenthal
      This paper presents a numerical method for analysing the aero-elastic response of bluff line-like structures subjected to turbulent wind. Simulating the buffeting response of line-like structures such as bridges and towers requires accurate modelling of atmospheric turbulence, the cross-sectional aerodynamic behaviour and the structural dynamics. Here the fluid–structure interaction problem is solved considering a three-dimensional structural model coupled with a series of two-dimensional Computational Fluid Dynamics simulation slices, utilising the Vortex Particle Method. The coupled set of simulation slices accounts for the three-dimensional dynamic characteristics of the structure and the turbulent inflow conditions. This pseudo three-dimensional approach is presented as an accurate, yet computationally cheaper alternative to fully three-dimensional simulations of the fluid–structure interaction problem. For the inflow conditions in each simulation slice, the characteristics of the turbulent wind are modelled through pseudo-random velocity time-histories that satisfy the mean velocity profile, spectral properties and spatial coherence of the three-dimensional turbulent wind assumed. The wind field is modelled through vorticity injected at the upstream boundary of the simulation domain. The different components of the method are presented and validated. Finally, the method is applied to the study of a cable-stayed bridge, and the results are validated against wind tunnel measurements.

      PubDate: 2017-05-01T15:56:01Z
      DOI: 10.1016/j.jfluidstructs.2017.04.001
      Issue No: Vol. 72 (2017)
       
  • The viscous torsional pendulum
    • Authors: Francesco Viola; François Gallaire
      Pages: 25 - 37
      Abstract: Publication date: July 2017
      Source:Journal of Fluids and Structures, Volume 72
      Author(s): Francesco Viola, François Gallaire
      A disk that is free to rotate about its axis and connected to a torsional spring behaves as a damped oscillator when twisted and released. The initial elastic energy is periodically turned to kinetic energy and it gets progressively dissipated by the viscous friction exerted by the surrounding fluid. The subsequent oscillating motion is dictated by the fluid–solid interaction which is here solved numerically by coupling the second Euler’s law, that prescribes the disk’s rotation, to the Navier–Stokes equations, that govern the fluid’s motion. Two different regimes are observed: (i) a low-amplitude regime, where the phase lag between the twisting velocity and the viscous torque is equal to 3 π ∕ 4 and the instantaneous damping rate is constant; (ii) a higher amplitude regime, where the twisting velocity and the viscous torque are out of phase and the damping rate increases proportionally to the square root of the oscillation amplitude. These observations are rationalized through boundary layer theory applied in the vicinity of the disk, thus retrieving analytical expressions of the viscous torque available in the literature. By using a multiple scale technique, an explicit expression for the free decay of the disk torsional pendulum is obtained which well predicts the results of the numerical simulations without any tunable parameter.

      PubDate: 2017-05-26T19:50:10Z
      DOI: 10.1016/j.jfluidstructs.2017.04.005
      Issue No: Vol. 72 (2017)
       
  • Sharp interface immersed boundary methods and their application to
           vortex-induced vibration of a cylinder
    • Authors: Martin D. Griffith; Justin S. Leontini
      Pages: 38 - 58
      Abstract: Publication date: July 2017
      Source:Journal of Fluids and Structures, Volume 72
      Author(s): Martin D. Griffith, Justin S. Leontini
      The sharp interface immersed boundary method is assessed for suitability and accuracy in simulating flow-induced vibration, specifically the phenomenon of vortex-induced vibration (VIV) in the two-dimensional flow past an elastically-mounted cylinder. Inherent to immersed boundary methods are the spurious force oscillations observed when the immersed boundary moves across the underlying grid. This deficiency in immersed boundary methods is acute in flows featuring fully-coupled fluid–structure interaction, where these oscillations are fed directly back into the coupled system and have the potential to significantly affect the solution. Here, the immersed boundary method is tested and compared directly and in detail to an accurate and validated spectral-element method. The immersed boundary method performs well for the given problem, excepting a few cases, such as those featuring disordered vortex-shedding. A heuristic model is developed to analyze the frequency content of the observed spurious force oscillations and their potential to affect the global solution. A guide to the resolution required for spatial accuracy is proposed, that around 40 points should span the peak-to-peak distance of any significant oscillation.

      PubDate: 2017-05-12T09:39:03Z
      DOI: 10.1016/j.jfluidstructs.2017.04.008
      Issue No: Vol. 72 (2017)
       
  • Experimental and numerical studies of the pontoon effect on vortex-induced
           motions of deep-draft semi-submersibles
    • Authors: Mingyue Liu; Longfei Xiao; Yibo Liang; Longbin Tao
      Pages: 59 - 79
      Abstract: Publication date: July 2017
      Source:Journal of Fluids and Structures, Volume 72
      Author(s): Mingyue Liu, Longfei Xiao, Yibo Liang, Longbin Tao
      The vortex-induced motion (VIM) is a critical issue in mooring and riser system design for column-type deepwater platforms. As regards to deep-draft semi-submersibles (DDS), even though VIM is mainly excited by vortex shedding around columns, the large-volume pontoons beneath the columns are also responsible for the wake interference, implying a non-negligible influence on VIM behavior. An experimental study and three-dimensional numerical simulations were performed to analyze the pontoon effect on the VIM of two semi-submersibles and a four-column structure without pontoons. The numerical results using Detached Eddy Simulation (DES) are in good agreement with the experimental measurements obtained from the towing model tests. The present investigations indicate that the resonant phenomenon is observed for all configurations. However, the four-column structure without pontoons shows the most significant transverse responses and yaw motions at both 0°- and 45°-incidences owing to the largest fluctuating lift forces induced by the well-established wake. Additionally, the negative values of work done by the pontoons at all reduced velocities confirm their damping effect on the VIM response.

      PubDate: 2017-05-12T09:39:03Z
      DOI: 10.1016/j.jfluidstructs.2017.04.007
      Issue No: Vol. 72 (2017)
       
  • An algebraic expansion of the potential theory for predicting dynamic
           stability limit of in-line cylinder arrangement under single-phase fluid
           cross-flow
    • Authors: Mustapha Benaouicha; Franck Baj; Elisabeth Longatte
      Pages: 80 - 95
      Abstract: Publication date: July 2017
      Source:Journal of Fluids and Structures, Volume 72
      Author(s): Mustapha Benaouicha, Franck Baj, Elisabeth Longatte
      Flow-induced vibration in square cylinder arrangement under viscous fluid incompressible cross-flow is investigated in the present work. The purpose is to contribute to better modeling and understanding external fluid loads exerted on long thin cylinders inducing flow perturbations. Due to high flow confinement, thin cylinders may be subjected to strong vibrations, which may lead to dynamic instability development. A theoretical approach is developed to determine a stability criterion of the dynamical system. The influence of geometric, mechanical and flow parameters such as reduced velocity and pitch ratio is investigated. The proposed model is derived from the potential flow theory and enhanced through an algebraic phase lag model in order to predict the critical limit of the reduced velocity for a square cylinder arrangement submitted to an external in-line cross flow. A theoretical formulation of the total damping, including added damping in still fluid, the damping due to fluid flow and the damping derived from the phase shift between the fluid load and the tube displacement, is expressed. A function depending on fluid and structure parameters, such as reduced velocity, pitch ratio and Scruton number is thus obtained. It is shown that this function provides a prediction of the dynamic stability limit of the system for several ranges of the major parameters to be considered. The results are compared to experimental reference solutions and to those provided by other theoretical models. This work proposes a consistent original model based on a potential flow theory enriched by using an algebraic formulation based on standard physical assumptions from literature. The major advantage of this model is due to the fact that it is in the same time robust and very user-friendly from a computational point of view thanks to the potential framework. In order to describe fluid and solid dynamics in the domain, terms coming from the potential flow theory are estimated by using a finite element method and complementary terms acting on damping are obtained through an algebraic formulation. Therefore this is a convenient way to propose a hybrid numerical / algebraic model for predicting dynamic instability limit in cylinder arrangements.

      PubDate: 2017-05-22T10:34:06Z
      DOI: 10.1016/j.jfluidstructs.2017.04.004
      Issue No: Vol. 72 (2017)
       
  • On the numerical simulations of captive, driven and freely moving cylinder
    • Authors: Guilherme Feitosa Rosetti; Guilherme Vaz
      Abstract: Publication date: Available online 18 August 2017
      Source:Journal of Fluids and Structures
      Author(s): Guilherme Feitosa Rosetti, Guilherme Vaz
      This paper presents the application of turbulence and laminar–turbulent transition models and fluid–structure capabilities to address the flow and response of captive, driven and free moving rigid cylinder for several Reynolds numbers. An investigation on the performance of the turbulence modeling with k – ω SST is presented, verifying the modeling deficiencies for this flow. The Scale Adaptive Simulations (SAS) and the Local Correlation Transition Model (LCTM or γ − R e θ ), both combined with the SST, improved the agreement with experimental results for the captive cylinder flow. These studies also involve verification and validation exercises in order to quantify modeling errors of the results herein. In a second step, the use of SST with driven cylinder motions is presented, as well as with the SAS and LCTM. Finally, aiming at free-moving cylinder behavior, this work presents the study of different turbulence modeling practices for the free-moving cylinder in two degrees of freedom (DOF) with low mass ratio. The importance of turbulence effects on the moving cylinder in comparison with the fixed case is investigated. A natural conjecture is that the turbulence modeling strategy is less decisive when the cylinder is moving with driven motion and even less stringent for free motions, as the body response would filter most of the higher order turbulence effects. This issue is investigated as it would allow modeling simplifications in the application of CFD to a range of engineering problems.

      PubDate: 2017-09-02T10:14:38Z
      DOI: 10.1016/j.jfluidstructs.2017.06.013
       
  • Numerical study of the aerodynamics of a full scale train under turbulent
           wind conditions, including surface roughness effects
    • Authors: Crespo
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): J. García, J. Muñoz-Paniagua, A. Crespo
      A numerical simulation of the aerodynamic behavior of a full scale train under synthetic crosswind is presented. Both smooth and rough train surfaces are contemplated in this paper. The synthetic wind is defined based on the Kaimal spectrum, which is generated using Turbsim. The flow description is based on numerical simulations obtained using Large Eddy Simulation (LES) with the commercial code ANSYS-Fluent. Considering a very-high Reynolds number for our train model with LES requires the use of a wall function in the near-wall region. In this way, it is removed the need to resolve any turbulent eddies in the inner part of the wall layer, and the entire inner-layer dynamics are represented by a single value of the wall shear stress. The simulation gives a time history of the force and moments acting on the train; this includes averaged values, standard deviations and extreme values. Of particular interest are the spectra and admittances of the forces and moments. Comparisons are made with numerical and experimental results obtained for a small scale model fixed to the ground in a wind tunnel.

      PubDate: 2017-08-03T02:51:02Z
       
  • Wave energy parks with point-absorbers of different dimensions
    • Authors: Malin
      Abstract: Publication date: October 2017
      Source:Journal of Fluids and Structures, Volume 74
      Author(s): Malin Göteman
      An analytical model for point-absorbing wave energy converters connected to floats of different geometries and topologies is presented. The floats can be truncated cylinder or cylinder with moonpool buoys and have different outer radius, inner radius, draft, mass and can be connected to linear generators of different power take-off constants. The model is implemented into a numerical code where the input is measured time-series of irregular waves. After validation against benchmark software, the model is used to study optimal configurations of wave energy arrays consisting of different wave energy devices. It is shown that the total power absorption can be improved if the wave energy array consists of devices of different dimensions, and that a higher power-to-mass ratio can be achieved.

      PubDate: 2017-08-03T02:51:02Z
       
  • Vortex-induced vibration suppression of a main circular cylinder with two
           rotating control rods in its near wake: Effect of the rotation direction
    • Authors: Hongjun Zhu; Yue Gao
      Abstract: Publication date: Available online 24 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Hongjun Zhu, Yue Gao
      Rotating small control rods in the near wake of a circular cylinder is a combination of both passive and active control techniques. The effect of rotation direction of control rods on vortex-induced vibration (VIV) suppression is investigated numerically by computational fluid dynamics (CFD) models coupling with a fluid–structure interaction (FSI) computational method. Two small rods with diameter ratio of 0.06 are located symmetrically at 135°right behind the main cylinder, and the gap between the main cylinder and control rods is 0.09D. The Reynolds number and the reduced velocity are 3484 and 6.0, respectively. Five different rotation modes are considered including the no-rotating case. The results indicate that the presence of control rods changes the momentum and kinetic energy distribution. Placing stationary rods in this specific position can achieve a good suppression effect, and the effect is enhanced when the control rods are inward counter rotating. Inward counter-rotating rods facilitate the momentum injection from the outer flow into the boundary layer, resulting in the delay of boundary layer separation and the shift of separation point. Therefore, the wake becomes narrower. However, control rods rotating outwardly play a counterproductive role in flow control and the vibration is enhanced. Rotating rods upwardly and downwardly have almost the same vibration responses. The cross-flow vibration is suppressed while the in-line vibration is enhanced at these two mirrored cases.

      PubDate: 2017-08-03T02:51:02Z
      DOI: 10.1016/j.jfluidstructs.2017.07.004
       
  • Application of a high-order CFD harmonic balance method to nonlinear
           aeroelasticity
    • Authors: Weigang Yao; Simão Marques
      Abstract: Publication date: Available online 22 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Weigang Yao, Simão Marques
      An Aeroelastic-Harmonic Balance (A-HB) formulation of the Euler flow equations using a high-order spatial discretization scheme coupled with structural dynamic equations is proposed. The main objective of this new approach is to dramatically reduce the computational cost required to predict unsteady, periodic problems such as limit cycle oscillations (LCO). To this end, a new solver based on the Monotonicity Preserving limiter together with the AUSM + -up flux function is developed for the harmonic balance equations. The use of high-order CFD schemes allows the reduction of the number of degrees of freedom required to achieve a given desired accuracy, with respect to lower order schemes. In this paper, the reduction in degrees of freedom of the fluid system is exploited in the context of a CFD based Harmonic-Balance framework using a frequency updating procedure to determine the limit cycle conditions. The standard A-HB methodology has shown over one order of magnitude speed-up over time-marching methods; by employing the proposed high-order scheme in conjunction with coarser grids, the LCO computational time is halved without compromising accuracy.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.014
       
  • Numerical study of mean drift force on stationary flexible barge
    • Authors: Dong-Min Park; Jung-Hyun Kim; Yonghwan Kim
      Abstract: Publication date: Available online 22 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Dong-Min Park, Jung-Hyun Kim, Yonghwan Kim
      In this study, a fully coupled fluid–structure interaction model was used to compute the mean drift force on a flexible barge under various wave conditions. The fluid domain was solved using a time domain B-spline 3-D Rankine panel method. The structural domain was modeled using a shell-element-based 3-D finite element model. The fluid model was coupled with the 3-D FE model via eigenvectors. Seakeeping analysis of the flexible body was performed by the fully coupled model. In the computation of drift force, two approaches were employed: a near-field method and a far-field method. The near-field method included an extension of the rigid body formula in the flexible body formula. The far-field method used the same formula for the rigid body and the flexible body. To the knowledge of the authors, it was not easy to find validation data for the mean drift force on a flexible barge. Therefore, an indirect validation was conducted by comparison of numerical results using a different approach. As a test model, a virtual barge model was used. The motion and mean drift force on the rigid barge were compared with the results of a commercial software, WADAM. The mean drift force on the flexible barge was compared to the results of the near-field and far-field methods.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.011
       
  • Nonlinear aerodynamic and energy input properties of a twin-box girder
           bridge deck section
    • Authors: Zhitian Zhang; Xianxiong Zhang; Yongxin Yang; Yaojun Ge
      Abstract: Publication date: Available online 20 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Zhitian Zhang, Xianxiong Zhang, Yongxin Yang, Yaojun Ge
      By means of computational fluid dynamics (CFD), the nonlinear aeroelastic properties of a bridge deck configuration is investigated in this study in terms of amplitude-dependent flutter derivatives and indicial functions. The results are partially compared with experimental results. It shows that the concerned properties exhibit significant dependence on the motion amplitudes. Moreover, based on flutter derivatives, the nonlinear aerodynamic properties can be divided into two groups: the group with torsional amplitudes less or equal than 10°, and the one with amplitudes larger than 10°. Flow patterns around the section of the two groups differ substantially; one group remains an overall streamlined pattern with locally distributed vortices and detached flow, while the other shows fully detached flow with large vortices emerging and developing drastically. Dynamic load coefficients indicate that, as the motion amplitude increases, the smoothness of the hysteresis loops decreases, suggesting irregular fluctuations of the loads resulted from signature turbulence, which becomes progressively prominent. Energy trapping properties derived from indicial functions are expressed in terms of dimensionless coefficients, of which the results indicate there is no possibility of single-DOF flutter, and coupling between vertical and torsional motions is necessary for flutter instability. Moreover, by the analysis of the phase angles involved in coupling, it is indicated that symmetricity of vertical motion has to be consistent with that of torsional motion in the event of a coupled flutter.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.016
       
  • Effect of mass ratio on thrust production of an elastic panel pitching or
           heaving near resonance
    • Authors: Yang Zhang; Chunhua Zhou; Haoxiang Luo
      Abstract: Publication date: Available online 17 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Yang Zhang, Chunhua Zhou, Haoxiang Luo
      Flapping wings of aerial insects and undulating fins of fish typically experience significant elastic chordwise deformations, and such deformations have been shown in previous studies to be beneficial on force production and/or power efficiency for both types of animal locomotion. However, it is still not conclusive whether the resonant vibration plays a common role in these problems. For fish fins, passive deformations are predominantly due to the hydrodynamic force of the surrounding fluid, while for insect wings, the wing inertia becomes also important in driving the surface deformation in addition to the aerodynamic force. In the current study, we use a two-dimensional elastic panel pitching or heaving in a free stream as a model to represent the animal wings or fins. Bending rigidity of the panel and the flapping frequency are varied so that the panel flaps near or away from resonance of the coupled fluid–structure system. The results show that at low mass ratios where the fluid force is dominant over the panel inertia, or at intermediate mass ratios where the fluid force is comparable with the panel inertia, the system resonance significantly improves or maximizes the thrust force and also efficiency; in addition, thrust performance is improved around resonance for a wide range of flapping frequencies or Strouhal numbers. On the other hand, at high mass ratios where the panel inertia is dominant, the system resonance makes thrust production increasingly difficult and propulsion much less efficient. In conclusion, the role of resonant vibration in thrust production of flapping wings and fins depends on participation of the fluid inertia in the process.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.07.003
       
  • A linear numerical model for analysing the hydroelastic response of a
           flexible electroactive wave energy converter
    • Authors: Aurélien Babarit; Jitendra Singh; Cécile Mélis; Ambroise Wattez; Philippe Jean
      Abstract: Publication date: Available online 14 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Aurélien Babarit, Jitendra Singh, Cécile Mélis, Ambroise Wattez, Philippe Jean
      In this paper, a linear mathematical and numerical model for analysing the dynamic response of a flexible electroactive wave energy converter is described. The Wave Energy Converter (WEC) is a floating elastic tube filled with slightly pressurised sea water. It is made of Electroactive Polymers (EAPs). Under simplifying assumptions, a set of governing equations is formulated for the flow inside the tube, the flow outside the tube and the behaviour of the tube wall. By combining them, the evolution of the flow velocity in the tube can be written as a wave equation. The corresponding eigenmodes of vibration are calculated. Then, using spectral decomposition, the equation of motion for the response of the tube in waves is derived. Experiments were carried out on a scale model of the wave energy converter in the wave tank of Ecole Centrale de Nantes in 2011. Numerical results are compared with experimental results in regular waves, showing rather good agreement, which validates the model and the initial modelling assumptions. Finally, estimates are made for the energy performance of a possible prototype.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.003
       
  • Dynamic response of a horizontal plate dropping onto nonlinear freak waves
           using a fluid–structure interaction method
    • Authors: Hao Qin; Wenyong Tang; Hongxiang Xue; Zhe Hu
      Abstract: Publication date: Available online 13 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Hao Qin, Wenyong Tang, Hongxiang Xue, Zhe Hu
      Freak waves are giant surface waves with huge wave heights which can lead to severe slamming to ships and offshore structures. However, few researches have been conducted to investigate the wave impact of a dropping plate against nonlinear freak waves. In order to study this phenomenon and predict the structural response of the dropping plate, a 2-D numerical wave tank is built in which nonlinear freak waves based on the Peregrine breather solution are generated. By combining the fluid domain governed by the Navier–Stokes (N–S) equations and the structure domain discretized by the finite element method (FEM) in a fully-coupled way, the fluid–structure interaction (FSI) is considered. Wave impact of a horizontal plate dropping onto a nonlinear freak wave is simulated and the structural responses of the plate including wetted frequency, maximum deflection, vertical velocity and vibration mode are obtained and analyzed. The unique features of the impact caused by the nonlinear freak wave are revealed through the comparison with a regular-wave-induced impact case. Moreover, the effects of carrier wave amplitude, initial impact location and dropping distance are further investigated and discussed in detail respectively.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.012
       
  • Aeroelastic flutter analysis considering modeling uncertainties
    • Authors: Mikaela Lokatt
      Abstract: Publication date: Available online 13 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Mikaela Lokatt
      A method for efficient flutter analysis of aeroelastic systems including modeling uncertainties is presented. The aerodynamic model is approximated by a piece-wise continuous rational polynomial function, allowing the flutter equation to be formulated as a set of piece-wise linear eigenproblems. Feasible sets for eigenvalue variations caused by combinations of modeling uncertainties are computed with an approach based on eigenvalue differentials and Minkowski sums. The method allows a general linear formulation for the nominal system model as well as for the uncertainty description and is thus straightforwardly applicable to linearized aeroelastic models including both structural and aerodynamic uncertainties. It has favorable computational properties and, for a wide range of uncertainty descriptions, feasible sets can be computed in output polynomial time. The method is applied to analyze the flutter characteristics of a delta wing model. It is found that both structural and aerodynamic uncertainties can have a considerable effect on the damping trends of the flutter modes and thus need to be accounted for in order to obtain reliable predictions of the flutter characteristics. This indicates that it can be beneficial to allow a flexible and detailed formulation for both aerodynamic and structural uncertainties, as is possible with the present system formulation.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.017
       
  • Structural dynamic reanalysis method for transonic aeroelastic analysis
           with global structural modifications
    • Authors: Dongfeng Li; Qiang Zhou; Gang Chen; Yueming Li
      Abstract: Publication date: Available online 13 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Dongfeng Li, Qiang Zhou, Gang Chen, Yueming Li
      Transonic aeroelastic analysis is an important aspect of modern aircraft design. When the modeshapes changed for the structural stiffness or/and mass matrix variation, the structural model and aerodynamic model could be reconstructed to maintain accuracy. However, these reconstruction procedures have to be repeated every time when there is a change in the aircraft structure design, where each of these reconstructions takes a considerable time. In this paper, an automated procedure for transonic aeroelastic analysis method was proposed when the structural model parameters changed at global level. To manage thousands of calculations and makes more efficient and reliable calculations, the structural dynamic reanalysis method was employed to set up an automated procedure to link the aeroelastic solvers and structural design parameters without changing structural modal coordinates. The proposed automated procedure was illustrated and verified by the AGARD 445.6 wing aeroelastic model with different global level structural parameter variations. The results show that the automated procedure can accurately produce pulse responses corresponding to the mode excitations and the flutter characteristics of AGARD 445.6 wing in a very large modification range. The whole automated procedure is efficient and reliable in managing transonic aeroelastic analysis when structural parameters changed at global level.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.004
       
  • Dynamics of a hybrid morphing wing with active open loop vibrating
           trailing edge by time-resolved PIV and force measures
    • Authors: G. Jodin; V. Motta; J. Scheller; E. Duhayon; C. Döll; J.F. Rouchon; M. Braza
      Abstract: Publication date: Available online 13 July 2017
      Source:Journal of Fluids and Structures
      Author(s): G. Jodin, V. Motta, J. Scheller, E. Duhayon, C. Döll, J.F. Rouchon, M. Braza
      A quantitative characterization of the effects obtained by high frequency–low amplitude trailing edge actuation is presented. Particle image velocimetry, pressure and aerodynamic forces measurements are carried out on a wing prototype equipped with shape memory alloys and trailing edge piezoelectric-actuators, allowing simultaneously high deformations (bending) in low frequency and higher-frequency vibrations. The effects of this hybrid morphing on the forces have been quantified and an optimal actuation range has been identified, able to increase lift and decrease drag. The present study focuses more specifically on the effects of the higher-frequency vibrations of the trailing edge region. This actuation allows manipulation of the wake turbulent structures. It has been shown that specific frequency and amplitude ranges achieved by the piezoelectric actuators are able to produce a breakdown of larger coherent eddies by means of upscale energy transfer from smaller-scale eddies in the near wake. It results a thinning of the shear layers and the wake’s width, associated to reduction of the form drag, as well as a reduction of predominant frequency peaks of the shear-layer instability. These effects have been shown by means of frequency domain analysis and Proper Orthogonal Decomposition.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.015
       
  • Nonlinear dynamical behaviors of deploying wings in subsonic air flow
    • Authors: Wei Zhang; Lu-Lu Chen; Xiang-Ying Guo; Lin Sun
      Abstract: Publication date: Available online 13 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Wei Zhang, Lu-Lu Chen, Xiang-Ying Guo, Lin Sun
      In recent years, the morphing wing, which is able to improve the lift–drag characteristics of the aircraft by changing wingspans and aspect ratios, has become a popular research issue. However, aeroelasticity is still a bottleneck for the development of morphing wings. The development of the aerodynamic calculations of deploying wings in subsonic air flow will be further promoted by this research. In this paper, we consider the aerodynamics of a deploying wing and investigate the nonlinear dynamic behaviors of the deploying wing. Under the flow condition of ideal incompressible fluid, the flow field is a potential field and the potential function must satisfy the Laplace linear equation and the superposition principle. When the thickness, curvature and angle of attack of the airfoil are small, the thin airfoil theory can be used to calculate the effects of the mean camber line to obtain the circulation distribution of the deploying wings in subsonic air flow. The steady aerodynamic lift on the deploying wing is derived by using the Kutta–Joukowski lift theory. Then, the aerodynamic lift is applied on a deploying wing, which is modeled as a cantilevered thin shell deploying in the axial direction. The nonlinear partial differential governing equations of motion for the deploying cantilevered thin shell subjected to the aerodynamic force in subsonic air flow are established based on Hamilton’s principle. The time-varying dependent vibration mode-shape functions are chosen using the boundary conditions, and then the Galerkin method is employed to transform the partial differential equation into two time-varying nonlinear ordinary differential equations. Numerical simulations are performed for the nonlinear dynamic responses of the deploying wing subjected to the aerodynamic force, and then the influence of different parameters, including the extending velocity and disturbance velocity, on the stability of the wing are analyzed. The effects of deploying velocities on the nonlinear vibrations of the first-order and second-order modes for the deploying wing are studied.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.04.006
       
  • A discrete-modules-based frequency domain hydroelasticity method for
           floating structures in inhomogeneous sea conditions
    • Authors: Wei Wei; Shixiao Fu; Torgeir Moan; Ziqi Lu; Shi Deng
      Abstract: Publication date: Available online 13 July 2017
      Source:Journal of Fluids and Structures
      Author(s): Wei Wei, Shixiao Fu, Torgeir Moan, Ziqi Lu, Shi Deng
      Based on the three-dimensional (3D) potential theory and finite element method (FEM), this paper proposes a new numerical method for hydroelastic predictions of floating structures in inhomogeneous seabed and wave field conditions. The continuous floating structure is first discretized into rigid modules connected by elastic beams. The motion equations of the entire floating structure are established according to the six degrees of freedom (6DOF) motions of each module by coupling the hydrodynamics of the modules with the structural stiffness matrix of the elastic beams in the frequency domain. By applying different wave excitation forces onto different modules, this discrete-modules-based method then uniquely realizes application of various wave excitation forces onto different modules of the structures in inhomogeneous waves. The hydroelastic responses of a plate and a Wigley hull under an even and uneven seabed using the proposed method are verified against the results from the published model tests and the conventional 3D hydroelastic method. Finally, the effects of inhomogeneous waves on the distributions of the bending moment, shear force and vertical displacements of the freely floating plate are investigated. The results show that the inhomogeneity of waves may induce about 2 ∼ 3 times increase of the force responses in a specific wave frequency.

      PubDate: 2017-07-23T01:29:04Z
      DOI: 10.1016/j.jfluidstructs.2017.06.002
       
  • Numerical study on the influence of acoustic natural frequencies on the
           dynamic behaviour of submerged and confined disk-like structures
    • Authors: Matias Bossio; David Alexandre Presas David Ramos Martin Eduard Egusquiza
      Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): Matias Bossio, David Valentín, Alexandre Presas, David Ramos Martin, Eduard Egusquiza, Carme Valero, Mònica Egusquiza
      The dynamic response of disks has been deeply studied in the last years given that their dynamic characteristics present similarities with more complex disk-like structures used in real engineering applications, such as hydraulic turbine runners. Because of disk-like structures could present fatigue damage or critical failures as a result of resonance conditions, it is of paramount importance to determine their natural frequencies. The dynamic response of disk-like structures is heavily affected by the added mass effect when they are surrounded by a heavy fluid. This added mass is greatly affected by the proximity of walls. Furthermore, the surrounding fluid cavity has its own natural frequencies and mode shapes, called acoustic natural frequencies and acoustic mode-shapes. All studies of submerged and confined disks have been carried out considering that the acoustic natural frequencies of the surrounding fluid cavity are much higher than the natural frequencies of the disk, so they do not affect each other. However, in some cases the acoustic natural frequencies are close to the natural frequencies of the submerged structure, which can be affected considerably. This case has not been deeply discussed yet. In this paper, the influence of the acoustic natural frequencies of a cylindrical fluid cavity on the natural frequencies of a disk has been analysed numerically. First, the effect of the added mass of the fluid has been estimated when the acoustic natural frequencies of the fluid cavity are much higher than the natural frequencies of the disk. For this case, different geometrical and material parameters have been considered. Then, the parameters that affect the acoustical natural frequencies of the fluid cavity have been identified. Finally, the case with acoustic natural frequencies close to the structural natural frequencies is studied in detail and the affectation between both is discussed. All the results presented in this paper have been dimensionless in order to be used for a wide range of disk-like structures. Therefore, with this study it is possible to identify for which conditions the dynamic response of a generic disk-like structure will be affected by the acoustic natural frequencies of its surrounding fluid cylindrical cavity.

      PubDate: 2017-06-21T08:52:35Z
       
  • Prediction of quarter-wave instability in direct spring operated pressure
           relief valves with upstream piping by means of CFD and reduced order
           modelling
    • Abstract: Publication date: August 2017
      Source:Journal of Fluids and Structures, Volume 73
      Author(s): I. Erdődi, C. Hős
      This paper focuses on modelling the dynamic instability (flutter/chatter) of gas-service direct spring operated pressure relief valves (DSOPRV) due to the acoustic coupling between the valve body dynamics and the upstream piping. Previous studies have shown through reduced order models that there exists a critical inlet pipe length beyond which self-excited vibrations occur due to the presence of a quarter standing wave in the upstream piping. However, to allow analytical computations and simple design equations, these reduced-order models relied on quasi-steady assumptions for the estimation of the discharge coefficient and the fluid force acting on the valve body. This paper proposes two CFD-based methods for the analysis of the fluid forces and valve stability: firstly, steady-state CFD runs were performed to verify the assumptions of the reduced order models and also to increase their accuracy. Secondly, dynamic CFD simulations using deforming mesh technology were conducted, with which the valve response can be resolved with high fidelity including also transient fluid–structure interactions. Comparing the results of the two approaches verify the use of the reduced-order models for stability predictions.

      PubDate: 2017-06-06T13:25:12Z
       
 
 
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