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  Subjects -> ENGINEERING (Total: 2268 journals)
    - CHEMICAL ENGINEERING (190 journals)
    - CIVIL ENGINEERING (183 journals)
    - ELECTRICAL ENGINEERING (103 journals)
    - ENGINEERING (1201 journals)
    - ENGINEERING MECHANICS AND MATERIALS (380 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (67 journals)
    - MECHANICAL ENGINEERING (89 journals)

CIVIL ENGINEERING (183 journals)                     

Showing 1 - 183 of 183 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: 35)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 28)
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: 2)
ATBU Journal of Environmental Technology     Open Access   (Followers: 4)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 6)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 10)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 4)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 4)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 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: 12)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 11)
Case Studies in Structural Engineering     Open Access   (Followers: 9)
Cement and Concrete Composites     Hybrid Journal   (Followers: 17)
Challenge Journal of Concrete Research Letters     Open Access   (Followers: 2)
Challenge Journal of Structural Mechanics     Open Access   (Followers: 5)
Change Over Time     Full-text available via subscription   (Followers: 2)
Civil and Environmental Engineering     Open Access   (Followers: 7)
Civil And Environmental Engineering Reports     Open Access   (Followers: 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: 10)
Civil Engineering Dimension     Open Access   (Followers: 8)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 265)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 11)
Computers & Structures     Hybrid Journal   (Followers: 36)
Concrete Research Letters     Open Access   (Followers: 6)
Construction Economics and Building     Open Access   (Followers: 2)
Construction Engineering     Open Access   (Followers: 9)
Construction Management and Economics     Hybrid Journal   (Followers: 22)
Construction Science     Open Access   (Followers: 4)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access   (Followers: 2)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal   (Followers: 1)
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 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: 9)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 16)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access  
Frontiers in Built Environment     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 4)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotechnik     Hybrid Journal   (Followers: 3)
Géotechnique Letters     Hybrid Journal   (Followers: 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: 14)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 9)
International Journal of Geo-Engineering     Open Access   (Followers: 3)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Masonry Research and Innovation     Hybrid Journal   (Followers: 1)
International Journal of Pavement Research and Technology     Open Access   (Followers: 5)
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: 12)
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: 4)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 4)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 24)
Journal of Construction Engineering     Open Access   (Followers: 7)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 19)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 8)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 4)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 6)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 2)
Journal of Green Building     Full-text available via subscription   (Followers: 11)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 13)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 21)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 5)
Journal of Marine Science and Engineering     Open Access   (Followers: 1)
Journal of Materials and Engineering Structures     Open Access   (Followers: 5)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 10)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 11)
Journal of Performance of Constructed Facilities     Full-text available via subscription   (Followers: 4)
Journal of Pipeline Systems Engineering and Practice     Full-text available via subscription   (Followers: 7)
Journal of Rehabilitation in Civil Engineering     Open Access   (Followers: 3)
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 40)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Sustainable Architecture and Civil Engineering     Open Access   (Followers: 3)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the Civil Engineering Forum     Open Access  
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 4)
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil dan Perencanaan     Open Access   (Followers: 1)
Konstruksia     Open Access  
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 2)
Latin American Journal of Solids and Structures     Open Access   (Followers: 4)
Materiales de Construcción     Open Access  
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 3)
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 17)
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 7)
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 2)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 4)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 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)
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: 10)
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: 13)
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  [3048 journals]
  • Model-less forecasting of Hopf bifurcations in fluid-structural systems
    • Authors: Amin Ghadami; Carlos E.S. Cesnik; Bogdan I. Epureanu
      Pages: 1 - 13
      Abstract: Publication date: January 2018
      Source:Journal of Fluids and Structures, Volume 76
      Author(s): Amin Ghadami, Carlos E.S. Cesnik, Bogdan I. Epureanu
      Predicting critical transitions and post-transition dynamics of complex systems is a unique challenge. In this paper, a novel approach is introduced to forecast Hopf bifurcations and the post-bifurcation dynamics of nonlinear fluid-structural systems. The forecasting method is model-less and uses measurements of the system response collected only in the pre-bifurcation regime. To demonstrate the method, it is applied to a cantilever high aspect ratio wing exposed to gust loads as perturbations. To generate surrogate measurements required for forecasting bifurcations in this large-dimensional complex system, a nonlinear strain-based finite element formulation coupled with unsteady aerodynamics is used to model the fluid–structure interaction. Results show that the method successfully forecasts the linear flutter speed and the amplitude of the limit cycle oscillations that occur in the post-bifurcation regime. The procedure is shown to be time efficient, model-less, and to require only few measurements, which makes the proposed forecasting method a unique tool for nonlinear analysis of complex systems.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

      PubDate: 2017-11-17T07:12:21Z
      DOI: 10.1016/j.jfluidstructs.2017.10.016
      Issue No: Vol. 76 (2017)
       
  • 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)
       
  • Effects of oncoming flow conditions on the aerodynamic forces on a
           cantilevered square cylinder
    • Authors: Hanfeng Wang; Xiaoyan Zhao; Xuhui He; Yu Zhou
      Pages: 140 - 157
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Hanfeng Wang, Xiaoyan Zhao, Xuhui He, Yu Zhou
      The aerodynamic forces on a cantilevered square cylinder with a height-to-width ratio (H/d) of 5 in a crossflow were experimentally investigated in a closed-loop low-speed wind tunnel. The freestream oncoming flow velocity ( U ∞ ) ranged from 5 to 45 m/s, corresponding to Reynolds numbers, based on U ∞ and d, of 0.68 × 105 to 6.12 × 105. Two different oncoming flow conditions were tested. In case 1, the majority of the cylinder span was in the uniform flow, except the lower 1d which was immersed in a thin turbulent boundary layer; in case 2, the tested cylinder was completely immersed in a turbulent boundary layer. In both cases, the Reynolds number had a negligible effect on the aerodynamic forces of the cylinder. The predominant vortex shedding frequency was constant along the cylinder span, regardless of the thickness and nature of the boundary layer. In case 1, the lift fluctuated periodically with a large amplitude or did not exhibit obvious periodicity, which correspond to the anti-symmetric and symmetric vortex shedding modes, respectively. Proper orthogonal decomposition (POD) analysis showed that, in case 2, anti-symmetric vortex shedding tends to occur, instead of the symmetric mode, thus resulting in a larger fluctuating lift than that observed case 1.

      PubDate: 2017-09-26T12:37:13Z
      DOI: 10.1016/j.jfluidstructs.2017.09.004
      Issue No: Vol. 75 (2017)
       
  • Analysis for wave power capture capacity of two interconnected floats in
           regular waves
    • Authors: Siming Zheng; Yongliang Zhang
      Pages: 158 - 173
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Siming Zheng, Yongliang Zhang
      The most representative of raft-type wave energy converters (WECs) is one composed of two interconnected floats, which uses the relative rotation between the floats to drive a Power Take-Off (PTO) system, achieving power capture from ocean waves. This paper presents a fundamental investigation into the wave power capture capacity of two interconnected floats with arbitrary float length. Linear hydrodynamics of the interconnected floats and a linear PTO system are employed, which enables us to carry out a frequency-domain analysis. Analytical formulas are derived of an optimized PTO damping and PTO stiffness/inertia for maximizing wave energy conversion in regular waves with/without consideration of relative rotary motion constraints due to the restraints of pump stroke or/and collision problem between the floats. The analytical model is then employed to examine the influence of fore-and-aft float length ratio, PTO system and float rotary inertia radius on the power capture capability of the two interconnected floats. It is concluded that for general wave conditions and specified total float length, two interconnected floats with the fore one properly shorter than the aft one possess high capacity in power absorption.

      PubDate: 2017-10-04T09:24:24Z
      DOI: 10.1016/j.jfluidstructs.2017.08.010
      Issue No: Vol. 75 (2017)
       
  • On lift and drag decomposition coefficients in a model reduction framework
           using pressure-mode decomposition (PMD) analysis
    • Authors: Haroon Imtiaz; Imran Akhtar
      Pages: 174 - 192
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Haroon Imtiaz, Imran Akhtar
      Proper orthogonal decomposition (POD) has been extensively used for developing reduced-order models (ROM) in fluid mechanics. In most of the research, velocity POD modes are employed for analysis while there is less focus on using pressure POD modes. In fact, pressure POD modes can be beneficial to gain physical insight to the aerodynamic forces acting on a structure. In this study, we simulate the flow past a circular cylinder and compute the velocity and pressure POD modes from the data ensemble. We then perform the novel process of pressure mode decomposition (PMD). We consider the localized pressure POD modes on the cylinder surface, integrate each mode on the cylinder surface, and decompose them into normal and streamwise components, namely lift (LDC) and drag (DDC) decomposition coefficients, respectively. The LDC and DDC are scalar quantities and are independent of spatial coordinates. These coefficients provide insight to the contribution of each mode in the development of aerodynamic forces. The lift and drag coefficients are expanded in a Galerkin fashion using the decomposition coefficients. The temporal coefficients are computed through a mapping function based on a quadratic stochastic estimator. The main contribution and strength of our research is the PMD analysis and to develop an efficient ROM for aerodynamic forces which shows promising results for circular and elliptic cylinders.

      PubDate: 2017-10-04T09:24:24Z
      DOI: 10.1016/j.jfluidstructs.2017.09.003
      Issue No: Vol. 75 (2017)
       
  • Two-dimensional wave radiation and diffraction problems in a flat or
           sloping seabed environment
    • Authors: Aichun Feng; Wei Bai; W.G. Price
      Pages: 193 - 212
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Aichun Feng, Wei Bai, W.G. Price
      Two-dimensional water wave problems are investigated in an environment with a flat or sloping rigid seabed adopting a continuous Rankine source method. All the fluid domain surfaces, that is the free, body and seabed surfaces, are discretized using continuous panels. These panels are positioned exactly on the fluid boundary surfaces and no desingularization technique is required. A new seabed source panel distribution method is developed to accommodate both symmetric and asymmetric seabed profiles. To validate the numerical model comparisons are made with published findings from other mathematical models and experimental data. The presence of a sloped seabed alters the symmetry of the fluid domain, causing wave reflection and shoaling, and therefore, significantly affects the hydrodynamic characteristics of water wave problems. The influence of these topographies on the responses in all three degrees of freedom (heave, sway and roll) of a rigid floating body are investigated and discussed accounting for wave radiation and diffraction problems.

      PubDate: 2017-10-04T09:24:24Z
      DOI: 10.1016/j.jfluidstructs.2017.09.001
      Issue No: Vol. 75 (2017)
       
  • Effect of motion trajectory on the aerodynamic performance of a flapping
           airfoil
    • Authors: Shuchao Yang; Chen Liu; Jie Wu
      Pages: 213 - 232
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): Shuchao Yang, Chen Liu, Jie Wu
      In this paper, the influence of the motion trajectory on the aerodynamic performance of a flapping airfoil is numerically investigated. The airfoil synchronously performs a rotating motion (pitch), a horizontal motion (surge) and a vertical motion (plunge). The motion trajectory can be modified by changing the relative frequency of surging motion ( k ) , the amplitude of surging motion ( l m ) and the phase difference between pitch and surge ( φ ). To perform the numerical simulations, a NACA0012 airfoil is employed. A low Reynolds number ( Re = 500 ) is selected for small creatures and flapping MAVs. As compared with the traditional motion, it is observed that the figure-of-eight motion trajectory has a promotion for the thrust and propulsive efficiency, and the lift is improved when the relative surging frequency k is an odd number with the specified phase difference. In addition, the phenomenon of multiple vortices and resultant vortex capture appears when the surging motion is added, which is helpful for the improvement of thrust.

      PubDate: 2017-10-04T09:24:24Z
      DOI: 10.1016/j.jfluidstructs.2017.08.009
      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)
       
  • Achieving hover equilibrium in free flight with a flexible flapping wing
    • Authors: James Bluman; Chang-kwon Kang
      Abstract: Publication date: November 2017
      Source:Journal of Fluids and Structures, Volume 75
      Author(s): James Bluman, Chang-kwon Kang
      Recent discoveries in the fields of flapping wing aerodynamics and fluid–structure interaction have demonstrated that flexible wings can generate more lift than rigid wings. However, the implications of wing flexibility on the flight dynamics of flapping wing flyers is still an open research question. The main difficulty is that the free flight of flapping flyers with flexible wings is a result of the dynamic balance between unsteady aerodynamics, fluid–structure interaction, and flight dynamics. This study presents a fully coupled three-way flight simulator that solves the two-dimensional Navier–Stokes equations, tightly coupled to the Euler–Bernoulli beam equations of the wing and the nonlinear multi-body equations of motion for the dynamics at the fruit fly scale. A novel trim algorithm is used to determine the hover equilibrium in the longitudinal plane. The control inputs, i.e. the flapping amplitude, stroke plane angle, and flapping offset angle as well as the initial conditions are determined that effectively eliminate average body accelerations to less than 3% of gravitational acceleration. The resulting hover equilibrium control parameters flapping amplitude, stroke plane angle and the total power required agree well with the biological observation of fruit flies. Body oscillations in hovering free flight affect the flexible response of the wing compared to prescribed body motion without oscillation. The affected wing motion reduces the lift coefficient by up to 8.7% for the stiffest wing, necessitating slightly different control inputs to achieve trim. Finally, the power required to achieve hover equilibrium is 32%–94% lower for flexible wings than for rigid wings that are actively rotated to match the same passive pitch schedule.

      PubDate: 2017-09-26T12:37:13Z
       
  • 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
       
  • 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
       
 
 
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