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Nondimensional frequency scaling of aerodynamically-tensioned membranes

JOURNAL OF fluidS AND structureS 2014年 48卷 14-26页

作者： Zhang, Zheng Hopper, Logan Wrist, Andrew Hubner, James P. Ukeiley, Lawrence Univ Alabama Dept Aerosp Engn & Mech Tuscaloosa AL 35487 USA Univ Florida Dept Mech & Aerosp Engn Gainesville FL 32611 USA

Membrane wings have applications that involve low Reynolds number flyers such as micro air vehicles. The time-averaged and time-dependent deformations of the membrane affect the aerodynamic characteristics of the wing, primarily in the region beyond the maximum aerodynamic efficiency of the wing. This paper investigates an appropriate nondimensional vibration frequency scaling of a spanwise tensioned membrane with free (unattached) leading and trailing edges at low Reynolds numbers relative to nondimensional aeroelastic parameters. Silicone rubber membranes with varying spanwise pre-tension, aerodynamic tension (due to wing angle-of-attack and flow dynamic pressure), modulus of elasticity, span, and thickness are studied. Experimental results are compared to a proposed scaling that simplifies the aerodynamic loading as a uniform pressure distribution acting on the membrane. Data is further compared and discussed relative to previous published results of membrane wings with finite wing spans (three-dimensional flow) and fixed (rigid) leading edges. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Membrane wings fluid-structure interaction Frequency scaling Aeroelastic scaling Low Reynolds number flow

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

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INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS 2014年第0期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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Mixing layer resonance under high-speed stream forcing

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JOURNAL OF SOUND AND VIBRATION 2014年第24期333卷 6453-6473页

作者： Thomassin, Jean Mureithi, Njuki Duc Vo, Huu Pratt Whitney Canada Longueuil PQ Canada Ecole Polytech Dept Mech Engn BWC AECL NSERC Chair Fluid Struct Interact Stn Ctr Ville Montreal PQ H3C 3A7 Canada Ecole Polytech Dept Mech Engn Stn Ctr Ville Montreal PQ H3C 3A7 Canada

In the majority of fluid-structure interaction problems, the biggest challenge lies in the fundamental understanding of the flow physics. Forced mixing layers is an important phenomenon found in many cases of flow-induced vibrations and acoustics. The response of a mixing layer to high-speed stream acoustic forcing is investigated with a theoretical and experimental approach. Two different experiments demonstrating the fluid mechanic phenomenon are presented. The first experiment consists of a circular jet impinging on a vibrating plate. The second experiment demonstrates the mixing layer resonance in the context of a fluidelastic instability causing high-amplitude vibrations in gas turbine high-pressure compressor rotor blades. Both the plate and the adjacent blade vibration induce an acoustic feedback that propagates within the jet and blade tip clearance flow, respectively. The resonance was found to occur when the feedback wavelength matched either the jet-to-plate or the inter-blade distance. In both experimental cases, the resonance condition has been simply modeled by the coincidence of a 1D feedback wave, which propagates upstream at reduced velocity by the high-speed flow. The coupling between the jet induced mixing layer and the feedback wave is assumed to naturally occur when one of the wave crests reaches the separation edge. The objective of this study is to improve the understanding of the coupling mechanism between an emanating shear layer and the acoustic forcing originating within a fast flow stream. The study is based on a simplified analytical model in order to enlarge the current understanding of the mixing layer receptivity to the more specific case of its response to high-speed stream forcing. To identify the mixing layer resonant modes, an analytical resonance condition is proposed. It is found that the mixing layer response becomes spatially resonant for specific source locations downstream in the high-speed flow. The study also provides an a

关键词： RESONANCE NONLINEAR acoustics COUPLING reactions (Chemistry) DATA analysis fluid-structure interaction

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A mixed modal-differential quadrature method for free and forced vibration of beams in contact with fluid

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MECCANICA 2014年第3期49卷 535-564页

作者： Eftekhari, S. A. Jafari, A. A. KN Toosi Univ Technol Dept Mech Engn Tehran Iran

A simple and accurate mixed modal-differential quadrature formulation is proposed to study the dynamic behavior of beams in contact with fluid. Both free and forced vibration problems are considered. The proposed mixed methodology uses the modal technique for the structural domain while it applies the differential quadrature method (DQM) to the fluid domain. Thus, the governing partial differential equations of the beam and fluid are reduced to a set of ordinary differential equations in time. In the case of forced vibration, the Newmark time integration scheme is employed to solve the resulting system of ordinary differential equations. The proposed formulation, in general, combines the simplicity of the modal method and high accuracy and efficiency of the DQM. Its application is shown by solving some beam-fluid interaction problems. Comparisons with analytical solutions show that the present method is very accurate and reliable. To demonstrate its efficiency, the test problems are also solved using the finite element method (FEM). It is found that the proposed method can produce better accuracy than the FEM using less computational time. The technique presented in this investigation is general and can be used to solve various fluid-structure interaction problems.

关键词： Mixed modal-differential quadrature formulation Integral quadrature rule fluid-structure interaction Beams in contact with fluid Free and force vibration analysis Analytical solution

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Resonance of Free-Surface Waves Provoked by Floodgate Maneuvers

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JOURNAL OF HYDROLOGIC ENGINEERING 2014年第6期19卷 1124-1130页

作者： Triki, Ali Univ Sfax Engn Sch Sfax Sfax 3038 Tunisia

Prediction of damage caused by floodgate maneuvers is treated by the determination of factors amplifying the magnitude of generated damage. The identification of vulnerable areas is obtained by analogy with the water-hammer phenomenon in pressurized pipes. The numerical model is based on the Boussinesq assumption for transient flow in open channels and solved by the Mac-Cormack scheme. Transient flow concerns a rectangular channel where the initial steady state is uniform. Transient regime is provoked by the movement of a floodgate at the upstream extremity of the channel producing sinusoidal fluctuations of depth. A condition of floodgate closure is imposed at the downstream extremity. The applied excitation has permitted analysis of the fluid structure interaction, examination of pulsations provoking the resonance of the free-surface waves, and study of the evolution of depths according to time along the channel. According to the frequency of the movement of the floodgate at the upstream end, distortion of depth profiles or oscillations over these profiles may appear. The frequency value also has a significant effect on the flow depth evolution and can provoke the flooding of the channel.

关键词： fluid-structure interactions Boussinesq equations Surface waves Resonance Wave propagation fluid-structure interaction Boussinesq assumption Free-surface wave Prismatic channel Mac-Cormack scheme Resonance Wave propagation

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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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Slender-body theory for viscous flow via dimensional reduction and hyperviscous regularization

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MECCANICA 2014年第9期49卷 2153-2167页

作者： Giusteri, Giulio G. Fried, Eliot Univ Cattolica Sacro Cuore Dipartimento Matemat & Fis N Tartaglia I-25121 Brescia Italy Okinawa Inst Technol Grad Univ Math Soft Matter Unit Onna Son Okinawa 9040495 Japan

A new slender-body theory for viscous flow, based on the concepts of dimensional reduction and hyperviscous regularization, is presented. The geometry of flat, elongated, or point-like rigid bodies immersed in a viscous fluid is approximated by lower-dimensional objects, and a hyperviscous term is added to the flow equation. The hyperviscosity is given by the product of the ordinary viscosity with the square of a length that is shown to play the role of effective thickness of any lower-dimensional object. Explicit solutions of simple problems illustrate how the proposed method is able to represent with good approximation both the velocity field and the drag forces generated by rigid motions of the immersed bodies, in analogy with classical slender-body theories. This approach has the potential to open up the way to more effective computational techniques, since geometrical complexities can be significantly reduced. This, however, is achieved at the expense of involving higher-order derivatives of the velocity field. Importantly, both the dimensional reduction and the hyperviscous regularization, combined with suitable numerical schemes, can be used also in situations where inertia is not negligible.

关键词： Slender-body theory Hyperviscosity fluid-structure interaction Dimensional reduction

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FEM/wideband FMBEM coupling for structural-acoustic design sensitivity analysis

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2014年 276卷 1-19页

作者： Chen, Leilei Zheng, Changjun Chen, Haibo Univ Sci & Technol China GAS Key Lab Mech Behav & Design Mat Dept Modern Mech Hefei 230026 Anhui Peoples R China

A coupling algorithm based on the finite element method (FEM) and the wideband fast multipole boundary element method (wideband FMBEM) is proposed for acoustic fluid-structure interaction simulation and structural-acoustic design sensitivity analysis by using the direct differentiation method. The wideband fast multipole method (FMM), which is developed by combining the original FMM and the diagonal form FMM, is used to accelerate the calculation of the matrix vector products in boundary element analysis. The iterative solver generalized minimal residual method is applied to accelerate the calculation of the solution to the linear system of equations. The FEM/wideband FMBEM algorithm makes it possible to predict the effects of arbitrarily shaped vibrating structures on the sound field numerically. Numerical examples are presented to demonstrate the validity and efficiency of the proposed algorithm. (C) 2014 Elsevier B.V. All rights reserved.

关键词： fluid-structure interaction FEM Wideband FMBEM Design sensitivity analysis Direct differentiation method

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On the dynamics of a tandem of asynchronous flapping wings: Lattice Boltzmann-immersed boundary simulations

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PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2014年 410卷 276-286页

作者： De Rosis, Alessandro Univ Bologna Dept Agr Sci I-40127 Bologna Italy

In this paper, the flight performance of a tandem of symmetric flapping wings immersed in a viscous fluid is investigated. A harmonic motion is imposed to the wings which can travel only in the vertical direction. Specifically, the attention focuses on the role of the initial phase difference. The fluid domain is modeled through the lattice Boltzmann method. In order to account for the presence of the wings immersed in the lattice fluid background, the immersed boundary method is adopted. Once fluid forces acting upon the wings are computed, their position is updated by solving the equation of solid motion by the time discontinuous Galerkin method according to a strategy already validated by the author. A wide numerical campaign is carried out by varying the initial phase difference. Moreover, scenarios accounting for the presence of a lateral wind gust are shown. The flight conditions and performance are discussed for a wide set of configurations and compared with an in-sync configuration, showing that the wind gust reduces the performance in certain scenarios. (C) 2014 Elsevier B.V. All rights reserved.

关键词： fluid-structure interaction Lattice Boltzmann method Flapping wings Immersed boundary

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