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Non-linear vibrations and stability of a periodically supported rectangular plate in axial flow

INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS 2014年 66卷 54-65页

作者： Tubaldi, E. Alijani, F. Amabili, M. McGill Univ Dept Mech Engn Montreal PQ H3A 0C3 Canada

In the present study, the geometrically non-linear vibrations of thin infinitely long rectangular plates subjected to axial flow and concentrated harmonic excitation are investigated for different flow velocities. The plate is assumed to be periodically simply supported with immovable edges and the flow channel is bounded by a rigid wall. The equations of motion are obtained based on the von Karman non-linear plate theory retaining in-plane inertia and geometric imperfections by employing Lagrangian approach. The fluid is modeled by potential flow and the flow perturbation potential is derived by applying the Galerkin technique. A code based on the pseudo-arc-length continuation and collocation scheme is used for bifurcation analysis. Results are shown through bifurcation diagrams of the static solutions, frequency-response curves, time histories, and phase-plane diagrams. The effect of system parameters, such as flow velocity and geometric imperfections, on the stability of the plate and its geometrically non-linear vibration response to harmonic excitation are fully discussed and the convergence of the solutions is verified. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Non-linear vibrations fluid-structure interaction Plate Axial-flow

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Exact pressure integrations on submerged bodies in waves using a quadtree adaptive mesh algorithm

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN fluidS 2014年第10期76卷 632-652页

作者： Rodrigues, J. M. Guedes Soares, C. Univ Lisbon Inst Super Tecn Ctr Marine Technol & Engn CENTEC P-1049001 Lisbon Portugal

The development of an adaptive free surface, mesh cutting, methodology, in order to analytically integrate pressures on varying wet parts of partially submerged surfaces in the presence of waves, is presented. Given a function of free-surface elevation, the algorithm checks for the intersection of the body with the free surface and, based on user-defined parameters, modifies the initial mesh, by subdividing the elements where necessary and eliminating others, via a quadtree approach. Redundant sub-divisions, generated in the quad-division process, are partially eliminated, but the quadrilateral nature of the elements is always kept. The free-surface function must be single-valued and its definition domain simply connected. Hydrostatic and Froude-Krylov forces are computed exactly on each panel by means of analytical formulations, which are derived and presented, based on the theory of linear gravity waves and from applying Green's theorem. Copyright (c) 2014 John Wiley & Sons, Ltd.

关键词： fluid-structure interaction free surface incompressible flow marine hydrodynamics mesh adaptation mesh generation

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DES evaluation of near-wake characteristics in a shallow flow

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JOURNAL OF fluidS AND structureS 2014年 45卷 153-163页

作者： Nasif, G. Barron, R. M. Balachandar, R. Univ Windsor Dept Mech Automot & Mat Engn Windsor ON N9B 3P4 Canada Univ Windsor Dept Math & Stat Windsor ON N9B 3P4 Canada Univ Windsor Dept Civil & Environm Engn Windsor ON N9B 3P4 Canada

Three-dimensional numerical modeling using Detached Eddy Simulation (DES) based on unsteady Reynolds-Averaged Navier-Stokes (RANS) with the k-omega SST (Shear-Stress Transport) turbulence model has been carried out to evaluate the characteristics of a shallow wake flow. The shallow wake is generated by inserting a sharp-edged bluff body in the open channel flow. A horseshoe vortex is captured in front of the body, which stretches downstream and envelops the vortices that form part of the shear layers. The mean and instantaneous flow field characteristics in the wake are examined and compared at different downstream locations to evaluate the three-dimensional features in the flow. Streamwise positive directed velocity is observed in the wake centerline at horizontal planes close to the bed. Flow features hitherto not captured in experimental studies can be identified in sections parallel to the bed and body. A typical signature of three-dimensionality, upward ejection of fluid elements from the bed towards the free surface, is also observed in the wake. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Bluff body wake Shallow flow Numerical modeling DES fluid-structure interaction

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Numerical simulation of the interaction between flow and flexible nets

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JOURNAL OF fluidS AND structureS 2014年 45卷 180-201页

作者： Bi, Chun-Wei Zhao, Yun-Peng Dong, Guo-Hai Xu, Tiao-Jian Gui, Fu-Kun Dalian Univ Technol State Key Lab Coastal & Offshore Engn Dalian 116024 Peoples R China Zhejiang Ocean Univ Marine Sci & Technol Sch Zhoushan 316000 Peoples R China

A numerical approach is proposed to simulate the interaction between flow and flexible nets in steady current. The numerical approach is based on the joint use of the porous-media model and the lumped-mass model. The configuration of flexible nets can be simulated using the lumped-mass model and the flow field around fishing nets can be simulated using the porous-media model. Using an appropriate iterative scheme, the fluid-structure interaction problem can be solved and the steady flow field around flexible nets can be obtained. In order to validate the numerical models, the numerical results were compared with the data obtained from corresponding physical model tests. The comparisons show that the numerical results are in good agreement with the experimental data. Using the proposed numerical approach, this paper presents the flow field around a single flexible net and two flexible nets with a spacing distance. Both the configuration of the flexible nets and the flow velocity results are in accordance with those of the corresponding physical model tests. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Flexible fishing net Flow field fluid-structure interaction Numerical simulation

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The one-dimensional response of a water-filled double hull to underwater blast: Experiments and simulations

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INTERNATIONAL JOURNAL OF IMPACT ENGINEERING 2014年 63卷 177-187页

作者： Schiffer, A. Tagarielli, V. L. Univ London Imperial Coll Sci Technol & Med Dept Aeronaut London SW7 2AZ England

Laboratory-scale fluid structure interaction (FSI) experiments and finite element (FE) simulations are performed to examine the one-dimensional blast response of double-walled hulls, consisting of two skins sandwiching a layer of water. Both monolithic and sandwich designs are considered for the outer skin. Experiments are conducted in a transparent shock tube which allows measurements of water cavitation and hull response by high-speed photography. Experiments and FE predictions are found in good agreement and allow concluding that the impulse imparted to double hulls by underwater explosions can be dramatically reduced by employing the sandwich construction of the outer skin;such reductions are scarcely sensitive to the thickness of the water layer. (C) 2013 Published by Elsevier Ltd.

关键词： fluid-structure interaction Cavitation Sandwich plate Shock wave Finite element

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Improving Blood Flow Simulations by Incorporating Measured Subject-Specific Wall Motion

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CARDIOVASCULAR ENGINEERING AND TECHNOLOGY 2014年第3期5卷 261-269页

作者： Lantz, Jonas Dyverfeldt, Petter Ebbers, Tino Linkoping Univ Dept Sci & Technol Linkoping Sweden Linkoping Univ Dept Med & Hlth Sci Linkoping Sweden Linkoping Univ Ctr Med Image Sci & Visualizat CMIV Linkoping Sweden Swedish E Sci Res Ctr SeRC Linkoping Sweden

Physiologically relevant simulations of blood flow require models that allow for wall deformation. Normally a fluid-structure interaction (FSI) approach is used;however, this method relies on several assumptions and patient-specific material parameters that are difficult or impossible to measure in vivo. In order to circumvent the assumptions inherent in FSI models, aortic wall motion was measured with MRI and prescribed directly in a numerical solver. In this way is not only the displacement of the vessel accounted for, but also the interaction with the beating heart and surrounding organs. In order to highlight the effect of wall motion, comparisons with standard rigid wall models was performed in a healthy human aorta. The additional computational cost associated with prescribing the wall motion was low (17%). Standard hemodynamic parameters such as time-averaged wall shear stress and oscillatory shear index seemed largely unaffected by the wall motion, as a consequence of the smoothing effect inherent in time-averaging. Conversely, instantaneous wall shear stress was greatly affected by the wall motion;the wall dynamics seemed to produce a lower wall shear stress magnitude compared to a rigid wall model. In addition, it was found that if wall motion was taken into account the computed flow field agreed better with in vivo measurements. This article shows that it is feasible to include measured subject-specific wall motion into numerical simulations, and that the wall motion greatly affects the flow field. This approach to incorporate measured motion should be considered in future studies of arterial blood flow simulations.

关键词： Computational fluid dynamics Magnetic resonance imaging fluid-structure interaction Aorta Time averaged wall shear stress Prescribed wall motion

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Transient response of a plate-liquid system under an aerial detonation: Simulations and experiments

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COMPUTERS & structureS 2014年 133卷 18-29页

作者： Langlet, Andre William-Louis, Mame Girault, Gregory Pennetier, Olivier Univ Orleans PRISME EA4229 F-45072 Orleans France Univ Bretagne Sud LIMATB Ctr Rech F-56321 Lorient France

This paper presents a mixed numerical approach to model the blast waves generated by the detonation of a spherical stoichiometric mixture of propane and oxygen, impacting a plate-liquid system. The problem is split into two parts. The first calculation part relies on the modeling of the blast load and its propagation. Over-pressure distribution, in this part, is presented and reveals a very good level of agreement with experimental results. The time and space scales of the blast load data must be compatible with the plate-liquid system. This compatibility is ensured by an appropriate spatio-temporal interpolation technique. This technique is presented and its effectiveness and accuracy are demonstrated. The second part consists in modeling the response of the coupled plate-liquid system under the numerical blast load model. Experiments at reduced scale are carried out in two configurations in order to assess the effectiveness of this mixed numerical approach. Convincing results are obtained and discussed. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Blast wave Plate-liquid system fluid-structure interaction Cartesian methods Reduced scale experiments

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Computational simulation of the interactions between moving rigid bodies and incompressible two-fluid flows

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COMPUTERS & fluidS 2014年 94卷 1-13页

作者： Ghasemi, Amirmandi Pathak, Ashish Raessi, Mehdi Univ Massachusetts Dept Mech Engn Dartmouth NS Canada

We present a two-dimensional computational flow solver for simulation of two-way interactions between moving rigid bodies and two-fluid flows. The fluids are assumed to be incompressible and immiscible. The two-step projection method along with Graphics Processing Unit (GPU) acceleration is employed to solve the flow equations. The fluid-solid interaction is captured by using the fictitious domain method. A consistent mass and momentum scheme is implemented, which allows for simulation of multiphase flows characterized by large density ratios. The evolution of interfaces in the three-phase system is tracked by using the volume-of-fluid method with two scalar functions, representing the solid domain and one of the fluids. A geometrical approach is employed to reconstruct the interfaces in cells containing three phases and capture the intersection of phase interfaces (triple point). The performance and accuracy of the flow solver are assessed through a set of canonical test cases. Then, it is used to simulate the interactions between a free-floating buoy and waves generated by a bottom-hinged paddle in a wave tank. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Multiphase flow fluid-structure interaction Fictitious domain Multimaterial interfaces CPU acceleration Wave energy conversion

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ST and ALE-VMS methods for patient-specific cardiovascular fluid mechanics modeling

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MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES 2014年第12期24卷 2437-2486页

作者： Takizawa, Kenji Bazilevs, Yuri Tezduyar, Tayfun E. Long, Christopher C. Marsden, Alison L. Schjodt, Kathleen Waseda Univ Dept Modern Mech Engn Shinjuku Ku Tokyo 1698050 Japan Waseda Univ Waseda Inst Adv Study Shinjuku Ku Tokyo 1698050 Japan Univ Calif San Diego La Jolla CA 92093 USA Rice Univ Houston TX 77005 USA Los Alamos Natl Lab Los Alamos NM 87545 USA

This paper provides a review of the space-time (ST) and Arbitrary Lagrangian-Eulerian (ALE) techniques developed by the first three authors' research teams for patient-specific cardiovascular fluid mechanics modeling, including fluid-structure interaction (FSI). The core methods are the ALE-based variational multiscale (ALE-VMS) method, the Deforming-Spatial-Domain/Stabilized ST formulation, and the stabilized ST FSI technique. A good number of special techniques targeting cardiovascular fluid mechanics have been developed to be used with the core methods. These include: (i) arterial-surface extraction and boundary condition techniques, (ii) techniques for using variable arterial wall thickness, (iii) methods for calculating an estimated zero-pressure arterial geometry, (iv) techniques for prestressing of the blood vessel wall, (v) mesh generation techniques for building layers of refined fluid mechanics mesh near the arterial walls, (vi) a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape, (vii) a scaling technique for specifying a more realistic volumetric flow rate, (viii) techniques for the projection of fluid-structure interface stresses, (ix) a recipe for pre-FSI computations that improve the convergence of the FSI computations, (x) the Sequentially-Coupled Arterial FSI technique and its multiscale versions, (xi) techniques for calculation of the wall shear stress (WSS) and oscillatory shear index (OSI), (xii) methods for stent modeling and mesh generation, (xiii) methods for calculation of the particle residence time, and (xiv) methods for an estimated element-based zero-stress state for the artery. Here we provide an overview of the special techniques for WSS and OSI calculations, stent modeling and mesh generation, and calculation of the residence time with application to pulsatile ventricular assist device (PVAD). We provide references for some of the other special techniques. With results from earl

关键词： Cardiovascular fluid mechanics fluid-structure interaction cerebral aneurysms pulsatile ventricular assist devices stents ALE methods ST methods special techniques

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Dynamic analysis of AP1000 shield building for various elevations and shapes of air intakes considering FSI effects subjected to seismic loading

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PROGRESS IN NUCLEAR ENERGY 2014年 74卷 44-52页

作者： Zhao, Chunfeng Chen, Jianyun Xu, Qiang Dalian Univ Technol Inst Earthquake Engn Dalian 116024 Peoples R China

The shield building of AP1000 was designed to protect the steel containment vessel of nuclear power plants. When an accident releases mass energy to containment, natural circulation of air outside containment cools steel containment vessel by air intake and water drains by gravity to enhance cooling with evaporation. However, the air intake in the original design located around the upper corner of shield building may not be the optimal position of shield building. In the previous study, the influence of various elevations and shapes of air intake on natural frequency considering fluid-structure effects under different water levels has been performed. In the present study, three elevations and two shapes (rectangle and circle) of air intakes with 7.13, 64.75 and 58.21 m are established and expressed as location I, II and III, respectively. The influences of various elevations and shapes of air intake on the structural response and stress distribution of shield building considering fluid-structure effects under seismic loading are also performed to identify the optimal design for stress analysis to improve the passive cooling system for AP1000 and CAP1400 (in China) in the future. The results of structural analyses indicated that the von Mises stress of both rectangular and circular air intakes at the lower location were greater than that of the higher location, and the stress for circular air intake was less than that of rectangular air intake under seismic loading. In addition, the simulation result also indicated that an optimal elevation of air intake should be implemented around the location II of shield building with circular shape, and the original design of air intake located around the upper corner of shield building may not be the optimal arrangement. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： AP1000 shield building Gravity drain water tank Air intake fluid-structure interaction Acceleration time history Seismic loading

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