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Hamiltonian Dynamics of Several Rigid Bodies Interacting with Point Vortices

JOURNAL OF NONLINEAR SCIENCE 2014年第2期24卷 359-382页

作者： Weissmann, Steffen TU Berlin Inst Math Berlin Germany

We derive the dynamics of several rigid bodies of arbitrary shape in a two-dimensional inviscid and incompressible fluid, whose vorticity is given by point vortices. We adopt the idea of Vankerschaver et al. (J. Geom. Mech. 1(2): 223-226, 2009) to derive the Hamiltonian formulation via symplectic reduction from a canonical Hamiltonian system. The reduced system is described by a noncanonical symplectic form, which has previously been derived for a single circular disk using heavy differential-geometric machinery in an infinite-dimensional setting. In contrast, our derivation makes use of the fact that the dynamics of the fluid, and thus the point vortex dynamics, is determined from first principles. Using this knowledge we can directly determine the dynamics on the reduced, finite-dimensional phase space, using only classical mechanics. Furthermore, our approach easily handles several bodies of arbitrary shape. From the Hamiltonian description we derive a Lagrangian formulation, which enables the system for variational time integrators. We briefly describe how to implement such a numerical scheme and simulate different configurations for validation.

关键词： Point vortices fluid-structure interaction Variational integrator Cotangent bundle reduction

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Enhanced Vortex Shedding in a 183 m Industrial Chimney

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ADVANCES IN STRUCTURAL ENGINEERING 2014年第7期17卷 951-960页

作者： Belver, A. V. Koo, K. Iban, A. L. Brownjohn, J. M. W. Goddard, C. Ctr Tecnol CARTIF Valladolid 47151 Spain Univ Exeter Dept Engn Exeter Devon England Univ Valladolid Escuela Ingn Ind ITAP E-47011 Valladolid Spain Bierrum Int Ltd Barton Le Clay Beds England

This paper shows how numerical simulation can be used to explain the dynamic behaviour of two chimneys in close proximity. For similar wind speeds, the dynamic response of the leeward chimney depends on alignment of wind directions with a vector from the new to the old chimney. Evidence is presented that Enhanced Vortex Shedding (EVS) caused significant vibrations on the old 183 m high reinforced concrete chimney at Rugeley Power Station during several years of coexistence with its replacement. Strong vibrations were observed under certain conditions of wind speed and direction during construction of the new chimney, consistent with predictions of a performance study. To avoid excessive response of the old chimney during its final years of coexistence with the new one, a tuned mass damper (TMD) was installed together with a monitoring system to verify the effectiveness of the TMD. The monitoring system allowed confirming that vibration levels for winds from the south-west direction of the new chimney were higher than for similar wind speeds from other directions, a finding validated by numerical simulation using advanced computational fluid dynamics (CFD) and fluid-structure interaction (FSI) techniques.

关键词： CFD fluid-structure interaction vortex induced vibrations inline and staggered interference orbit plots

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Elastodynamics of a Two-Dimensional Square Lattice With Entrained fluid-Part I: Comparison With Biot's Theory

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JOURNAL OF VIBRATION AND ACOUSTICS-TRANSACTIONS OF THE ASME 2014年第2期136卷 021024页

作者： Dorodnitsyn, Vladimir Spadoni, Alessandro Ecole Polytech Fed Lausanne Inst Engn Mech CH-1015 Lausanne Switzerland

In the present paper, the performance of Biot's theory is investigated for wave propagation in cellular and porous solids with entrained fluid for configurations with well-known drained (no fluid) mechanical properties. Cellular solids differ from porous solids based on their relative density rho* < 0.3. The distinction is phenomenological and is based on the applicability of beam (or plate) theories to describe microstructural deformations. The wave propagation in a periodic square lattice is analyzed with a finite-element model, which explicitly considers fluid-structure interactions, structural deformations, and fluid-pressure variations. Bloch theorem is employed to enforce symmetry conditions of a representative volume element and obtain a relation between frequency and wavevector. It is found that the entrained fluid does not affect shear waves, beyond added-mass effects, so long as the wave spectrum is below the pores' natural frequency. One finds strong dispersion in cellular solids as a result of resonant scattering, in contrast to Bragg scattering dominant in porous media. Configurations with 0: 0001 <= rho* <= 1 are investigated. One finds that Biot's theory, derived from averaged microstructural quantities, well estimates the phase velocity of pressure and shear waves for cellular porous solids, except for the limit rho* -> 1. For frequencies below the first resonance of the lattice walls, only the fast-pressure mode of the two modes predicted by Biot's theory is found. It is also shown that homogenized models for shear waves based on microstructural deformations for drained conditions agree with Biot's theory.

关键词： Biot's theory poroelasticity cellular solids band structure fluid-structure interaction

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Dynamic responses and damages of water-filled cylindrical shell subjected to explosion impact laterally

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LATIN AMERICAN JOURNAL OF SOLIDS AND structureS 2014年第11期11卷 1924-1940页

作者： Gao, FuYin Ji, Chong Long, Yuan Song, KeJian PLA Univ Sci & Tech Coll Field Engn Beijing Peoples R China

An account is given of some principal observations made from a series of experiments in which metal cylindrical shells were subjected to lateral explosion impact by different TNT charge mass and stand-off distance. These cylindrical shells were filled with water in order to identify the main effects produced by the fluid-structure interaction. In comparison, the explosion impact experiments of the empty cylindrical shells were also carried out. The effects of TNT charge mass, stand-off distance, cylindrical shell wall thickness and filled fluid (water) on perforation and deformation of metal cylindrical shells were discussed, which indicated that water increased the wall strength of the cylindrical shells under explosion impact loading, and the buckling deformation and perforation of the cylindrical shell was significantly influenced by the presence of the water;blast-resistant property of the tube under explosive impact loading of 200g TNT charge was much excellent;deformation and damage of empty cylindrical shell were more sensitive to stand-off distance changed. ALE finite element method was employed to simulate the deformations and damages of empty and water-filled cylindrical shells under explosion impact loading. The experimental and computational results are in agreement, showing the validity of the computational scheme in complex fluid-structure interaction problems involving metal materials subjected to explosion impact. The results show that internal pressure of water will increase when subjecting to impact loading, the anti-blast ability of tube structure is significantly enhanced.

关键词： Mechanics of explosion Explosion impact fluid-structure interaction water-filled cylindrical shell Numerical simulation

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Modelling inertial effects in periodic fluid-structure systems with an homogenisation approach: Application to seismic analysis of tube bundles

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JOURNAL OF fluidS AND structureS 2014年 49卷 73-90页

作者： Broc, Daniel Sigrist, Jean-Francois CEA DEN DANS DM2SSEMT F-91191 Gif Sur Yvette France DCNS Res Dept Dynam Struct F-44620 La Montagne France

fluid-structure interaction (FSI) is of major importance when describing the dynamic behaviour of nuclear pressure vessels, since the presence of confined fluid strongly influences the response of structures when subjected to external loadings, such as a seismic loading. Accounting for FSI when performing the seismic analysis of nuclear reactors or steam generators can be done through the description of inertial effects, which are predominant in the low frequency domain. Finite element techniques are now of common use in design office to model coupled (quiescent) fluid-structure systems, using standard non-symmetric (u,p) or symmetric (u,p,phi)) coupled formulations. When considering complex systems such as a tube bundle in steam generators, producing a finite element model which includes tubes, fluid and structures is a tedious task which is out of reach in many practical applications. A homogenisation method has been proposed which allows FSI modelling of tube bundles: it has been successfully applied to a complex structure. In the aforementioned developments, focus was put on the mathematical and numerical aspects of the method, leaving out some questions regarding the physical interpretation of the calculations. In the present paper, a new insight on the homogenisation approach is exposed with the objective of proposing a formulation of the method based on physical considerations, leading to a correction of the homogenised problem. Enhancement of the method is discussed from an engineering standpoint: it allows for a wider range of applications in the nuclear industry. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Tube bundle Seismic analysis Added mass Homogenisation method

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An optical instrument based on defocusing for dynamic response model testing in water or wind tunnels

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OCEAN ENGINEERING 2014年 79卷 92-100页

作者： Huera-Huarte, Francisco J. Univ Rovira & Virgili Dept Mech Engn E-43007 Tarragona Spain

The design and performance of an optical measurement system that can be used for studying the three-dimensional dynamic response of flexibly mounted rigid or elastic bodies in laboratory facilities is presented. The photogrammetric technique implemented on the instrument is based on the defocusing principle, which was first introduced for three-dimensional (3D) robotic vision applications. The technique was later on applied for the measurement of seeded 3D flow velocity fields. The emphasis of this work is given to the design of the tool itself as well as to its validation by using an application that involves the dynamics of a spar floater in a water tank. The final purpose of this work is to produce a non-intrusive and accurate instrument for measuring the fluid-induced responses or deformations of bodies in laboratory facilities. The result is an optical tool that provides an accurate and better alternative to other traditional dynamic response measurement techniques used to study vortex-induced vibrations (VIV), wave-induced motions (WIM), etc. in water or wind tunnels. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Range-measurements Defocusing DPIV fluid-structure interaction Offshore engineering Water tunnel Wind tunnel

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Modelling dynamic behaviour and noise generation in gear pumps: Procedure and validation

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APPLIED ACOUSTICS 2014年 77卷 99-111页

作者： Mucchi, Emiliano Rivola, Alessandro Dalpiaz, Giorgio Univ Ferrara Engn Dept Ferrara I-44122 Ferrara Italy Univ Bologna DIEM Dept Mech Engn I-40136 Bologna Italy

The paper presents a methodology for noise and vibration analysis of gear pumps and its application to an external gear pump for automotive applications. The methodology addresses the use of a combined numerical model and experimental analyses. The combined model includes a lumped-parameter model, a finite-element model and a boundary-element model. The lumped-parameter (LP) model regards the interior parts of the pump (bearing blocks and gears loaded by the pressure distribution and the driving torque), the finite element (FE) model regards the external parts of the pump (casing and end plates), while the boundary element (BE) model enables the estimation of the emitted noise in operational conditions. Based on experimental evidences, attention has been devoted to the modelling of the pump lubricant oil: the fluid-structure interaction between the oil and pump casing was taken into account. In the case of gear pumps all these important effects have to be considered in the same model in order to take their interactions into account. The model has been assessed using experiments: the experimental accelerations and acoustic pressure measured in operational conditions have been compared with the simulated data coming from the combined LP/FE/BE model. The combined model can be considered a very useful tool for design optimisation. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： External gear pumps Vibro-acoustic analysis Experimental validation fluid-structure interaction

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Feedback stabilization of a simplified 1d fluid-particle system

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ANNALES DE L INSTITUT HENRI POINCARE-ANALYSE NON LINEAIRE 2014年第2期31卷 369-389页

作者： Badra, Mehdi Takahashi, Takeo Univ Toulouse 3 UMR CNRS 5219 IMT F-31062 Toulouse 9 France Univ PAU UMR CNRS 5142 LMAP F-64013 Pau France PAYS ADOUR F-64013 Pau France Inria F-54600 Villers Les Nancy France Univ Lorraine IECN UMR 7502 F-54506 Vandoeuvre Les Nancy France CNRS IECN UMR 7502 F-54506 Vandoeuvre Les Nancy France

We consider the feedback stabilization of a simplified Id model for a fluid structure interaction system. The fluid equation is the viscous Burgers equation whereas the motion of the particle is given by the Newton's laws. We stabilize this system around a stationary state by using feedbacks located at the exterior boundary of the fluid domain. With one input, we obtain a local stabilizability of the system with an exponential decay rate of order sigma < sigma(0). An arbitrary order for the exponential decay rate can be proved if a unique continuation result holds true or if two inputs are used to stabilize the system. Our method is based on general arguments for stabilization of nonlinear parabolic systems combined with a change of variables to handle the fact that the fluid domains of the stationary state and of the stabilized solution are different. (C) 2013 Elsevier Masson SAS. All rights reserved.

关键词： Feedback stabilization fluid-structure interaction Viscous Burgers equation

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A new three-dimensional variable-node finite element and its application for fluid-solid interaction problems

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2014年 281卷 81-105页

作者： Kang, Yong-Soo Kim, Jungdo Sohn, Dongwoo Kim, Jeong Ho Kim, Hyun-Gyu Im, Seyoung Korea Adv Inst Sci & Technol Dept Mech Engn Taejon 305701 South Korea Korea Maritime & Ocean Univ Coll Engn Div Mech & Energy Syst Engn Pusan 606791 South Korea Inha Univ Dept Aerosp Engn Inchon 402751 South Korea Seoul Natl Univ Sci & Technol Dept Mech & Automot Engn Seoul 139743 South Korea

A new three-dimensional variable-node element is proposed to achieve an efficient connection of non-matching interfaces between dissimilar finite element meshes. The variable-node elements at interfaces are compatible with conventional finite elements, and satisfy the interface conditions of continuity, and completeness across non-matching meshes. The present method thereby provides a seamless connection between dissimilar finite element meshes and a correct load transfer across non-matching interfaces. Therefore, it leads to an efficient approach for solving a class of problems involving the non-matching interfaces such as fluid solid interaction problems. Numerical examples are presented to show the effectiveness of the present method for solving fluid solid interaction problems with non-conforming interfaces, and the usefulness and application of the present method are discussed. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Variable-node elements Non-matching interface fluid-structure interaction Arbitrary Lagrangian-Eulerian formulation

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A simple tree swaying model for forest motion in windstorm conditions

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TREES-structure AND FUNCTION 2014年第1期28卷 281-293页

作者： Pivato, David Dupont, Sylvain Brunet, Yves INRA EPHYSE UR1263 F-33140 Villenave Dornon France

A simple tree swaying model, valid for windstorm conditions, has been developed for the purpose of simulating the effect of strong wind on the vulnerability of heterogeneous forest canopies. In this model the tree is represented as a flexible cantilever beam whose motion, induced by turbulent winds, is solved through a modal analysis. The geometric nonlinearities related to the tree curvature are accounted for through the formulation of the wind drag force. Furthermore, a breakage condition is considered at very large deflections. A variety of case studies is used to evaluate the present model. As compared to field data collected on three different tree species, and to the outputs of mechanistic models of wind damage, it appears to be able to predict accurately large tree deflections as well as tree breakage, using wind velocity at tree top as a forcing function. The instantaneous response of the modelled tree to a turbulent wind load shows very good agreement with a more complex tree model. The simplicity of the present model and its low computational time make it well adapted to future use in large-eddy simulation airflow models, aimed at simulating the complete interaction between turbulent wind fields and tree motion in fragmented forests.

关键词： fluid-structure interaction Modal analysis Tree motion Turbulent flow Wind damage Windstorm

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