An immersed smoothed point interpolation method using 3-node triangular background cells is proposed to solve 2D fluid-structure interaction problems for solids with large deformation/displacement placed in incompress...
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An immersed smoothed point interpolation method using 3-node triangular background cells is proposed to solve 2D fluid-structure interaction problems for solids with large deformation/displacement placed in incompressible viscous fluid. In the framework of immersed-type method, the governing equations can be decomposed into 3 parts on the basis of the fictitious fluid assumption. The incompressible Navier-Stokes equations are solved using the semi-implicit characteristic-based split scheme, and solids are simulated using the newly developed edge-based smoothed point interpolation method. The fictitious fluid domain can be used to calculate the coupling force. The numerical results show that immersed smoothed point interpolation method can avoid remeshing for moving solid based on immersed operation and simulate the contact phenomenon without an additional treatment between the solid and the fluid boundary. The influence from information transfer between solid domain and fluid domain on fluid-structure interaction problems has been investigated. The numerical results show that the proposed interpolation schemes will generally improve the accuracy for simulating both fluid flows and solid structures.
Numerical investigation is conducted into the nonlinear dynamic responses to fluid-structure interaction in deep-hole drilling shaft system. Based on the theories of pipes and tubes conveying fluid, the governing equa...
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Numerical investigation is conducted into the nonlinear dynamic responses to fluid-structure interaction in deep-hole drilling shaft system. Based on the theories of pipes and tubes conveying fluid, the governing equation of the drilling shaft system is obtained taking into account of the fluid-structure interaction and the effect of the motion constraints. The nonlinear partial differential governing equation of motion is discretized in modal space using the Galerkin method and then transformed into a set of ordinary different equations. Numerical solutions of these equations are then obtained using the fourth order Runge-Kutta method. The influence of the forcing frequency and the support constraints on the dynamic behaviors of the drilling shaft is examined. The nonlinear dynamic behaviors of the drilling shaft system are presented by the bifurcation diagram and phase diagram. It has been found that the magnitude of support stiffness and the number and position of support constraints have a significant influence on dynamic behaviors of the drilling shaft system. The study in the paper provides an effective guidance to maintain the stability of the BTA deep-hole drilling shaft system through selecting the favorable operation parameters in deep hole drilling process.
Understanding the interaction between the valves and walls of the heart is important in assessing and subsequently treating heart dysfunction. This study presents an integrated model of the mitral valve (MV) coupled t...
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Understanding the interaction between the valves and walls of the heart is important in assessing and subsequently treating heart dysfunction. This study presents an integrated model of the mitral valve (MV) coupled to the left ventricle (LV), with the geometry derived from in vivo clinical magnetic resonance images. Numerical simulations using this coupled MV-LV model are developed using an immersed boundary/finite element method. The model incorporates detailed valvular features, left ventricular contraction, nonlinear soft tissue mechanics, and fluid-mediated interactions between the MV and LV wall. We use the model to simulate cardiac function from diastole to systole. Numerically predicted LV pump function agrees well with in vivo data of the imaged healthy volunteer, including the peak aortic flow rate, the systolic ejection duration, and the LV ejection fraction. In vivo MV dynamics are qualitatively captured. We further demonstrate that the diastolic filling pressure increases significantly with impaired myocardial active relaxation to maintain a normal cardiac output. This is consistent with clinical observations. The coupled model has the potential to advance our fundamental knowledge of mechanisms underlying MV-LV interaction, and help in risk stratification and optimisation of therapies for heart diseases. (C) 2017 The Author(s). Published by Elsevier Ltd on behalf of IPEM.
Standard Arbitrary Lagrangian-Eulerian (ALE) methods for the simulation of fluid-structure interaction (FSI) problems fail due to excessive mesh deformations when the structural displacement is large. We propose a met...
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Standard Arbitrary Lagrangian-Eulerian (ALE) methods for the simulation of fluid-structure interaction (FSI) problems fail due to excessive mesh deformations when the structural displacement is large. We propose a method that successfully deals with this problem, keeping the same mesh connectivity while enforcing mesh alignment with the structure. The proposed Extended ALE Method relies on a variational mesh optimization technique, where mesh alignment with the structure is achieved via a constraint. This gives rise to a constrained optimization problem for mesh optimization, which is solved whenever *** quality deteriorates. The performance of the proposed Extended ALE Method is demonstrated on a series of numerical examples involving 2D FSI problems with large displacements. Two-way coupling between the fluid and structure is considered in all the examples. The FSI problems are solved using either a Dirichlet-Neumann algorithm, or a Robin-Neumann algorithm. The Dirichlet-Neumann algorithm is enhanced by an adaptive relaxation procedure based on Aitken's acceleration. We show that the proposed method has excellent performance in problems with large displacements, and that it agrees well with a standard ALE method in problems with mild displacement. (C) 2016 Elsevier Inc. All rights reserved.
This paper presents a two-dimensional immersed boundary method for fluid-structure-interaction with compressible multiphase flows involving large structure deformations. This method involves three important parts: flo...
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This paper presents a two-dimensional immersed boundary method for fluid-structure-interaction with compressible multiphase flows involving large structure deformations. This method involves three important parts: flow solver, structure solver and fluid-structure interaction coupling. In the flow solver, the compressible multiphase Navier-Stokes equations for ideal gases are solved by a finite difference method based on a staggered Cartesian mesh, where a fifth-order accuracy Weighted Essentially Non-Oscillation (WENO) scheme is used to handle spatial discretization of the convective term, a fourth-order central difference scheme is employed to discretize the viscous term, the third-order TVD Runge-Kutta scheme is used to discretize the temporal term, and the level-set method is adopted to capture the multi-material interface. In this work, the structure considered is a geometrically non-linear beam which is solved by using a finite element method based on the absolute nodal coordinate formulation (ANCF). The fluid dynamics and the structure motion are coupled in a partitioned iterative manner with a feedback penalty immersed boundary method where the flow dynamics is defined on a fixed Lagrangian grid and the structure dynamics is described on a global coordinate. We perform several validation cases ( including fluid over a cylinder, structure dynamics, flow induced vibration of a flexible plate, deformation of a flexible panel induced by shock waves in a shock tube, an inclined flexible plate in a hypersonic flow, and shock induced collapse of a cylindrical helium cavity in the air), and compare the results with experimental and other numerical data. The present results agree well with the published data and the current experiment. Finally, we further demonstrate the versatility of the present method by applying it to a flexible plate interacting with multiphase flows. (C) 2017 Elsevier Inc. All rights reserved.
作者：
Gish, L. A.US Naval Acad
Dept Naval Architecture & Ocean Engn 590 Holloway Rd Annapolis MD 21402 USA
Underwater implosion, the rapid collapse of a structure caused by hydrostatic pressure, is a fully coupled, highly dynamic and nonlinear fluid-structure interaction (FSI) problem. The primary motivation behind studyin...
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Underwater implosion, the rapid collapse of a structure caused by hydrostatic pressure, is a fully coupled, highly dynamic and nonlinear fluid-structure interaction (FSI) problem. The primary motivation behind studying implosion is the short-duration, high-pressure pulse generated in the surrounding water. This paper presents a simplified analytic method to estimate the energy in the pressure pulse, based on potential flow theory. The method accounts for the varying fluid pressure and accompanying FSI. The focus is on long, thin, unstiffened metallic cylindrical shells that collapse in mode 2. The implosion pulse energy is shown to be equal to the maximum system kinetic energy developed during collapse. The kinetic energy is calculated using an energy balance approach and analytic solutions for plastic energy dissipation and energy required to compress the internal air. The time-varying fluid pressure, and subsequently the work done by the fluid on the cylinder, is found using a novel explicit time-stepping methodology. The result is a pseudo-coupled analytic solution for the fluid pressure time history and implosion pulse energy. Solutions for pulse energy agree with RANS numerical simulations within 5%. Published by Elsevier Ltd.
fluid-structure interaction (FSI) phenomena are of interest in several engineering fields. It is highly desirable to develop computationally efficient models to predict the dynamics of FSI. The complexity of modeling ...
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fluid-structure interaction (FSI) phenomena are of interest in several engineering fields. It is highly desirable to develop computationally efficient models to predict the dynamics of FSI. The complexity of modeling lies in the highly non-linear response of both the fluid and structure. The current study proposes an overall model containing two blocks corresponding to a force model and a structural model. The force model consists of two submodels: one for the amplitude and one for the frequency, where the latter is composed of an input/output linear model and a non-linear corrector. The amplitude submodel and the non-linear corrector term in the frequency submodel are modeled using an Hammerstein-Wiener modeling technique in which the non-linear input and output functions are determined by training neural networks using a training dataset. The current model is tested on a well-known fluid-structure interaction problem: a suspended rigid cylinder immersed in a flow at a low Reynolds number regime that exhibits a non-linear behavior. First, a training dataset is generated for a given input profile using a high-fidelity numerical simulation and it is used to train the reduced-order model. Subsequently, the trained model is given a different input profile (i.e., a validation profile) to compare its predictive capability against the high-fidelity numerical simulation. The validation profile is significantly different from the one used for training. The predictive performance of the current reduced-order model is further compared with the results obtained from a reduced-order model that uses polynomial fitting. We demonstrate that the current model provides a superior performance for the validation profile, i.e., it results in a better prediction.
In this paper,we propose a new partitioned approach to compute fluidstructureinteraction(FSI)by extending the original direct-forcing technique and integrating it with the immersed *** fluid and structural equations ...
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In this paper,we propose a new partitioned approach to compute fluidstructureinteraction(FSI)by extending the original direct-forcing technique and integrating it with the immersed *** fluid and structural equations are calculated separately via their respective disciplinary algorithms,with the fluid motion solved by the immersed boundary method on a uniform Cartesian mesh and the structural motion solved by a finite element method,and their solution data only communicate at the fluid-structure *** computational framework is capable of handling FSI problemswith sophisticated structures described by detailed constitutive *** proposed methods are thoroughly tested through numerical simulations involving viscous fluid flow interacting with rigid,elastic solid,and elastic thin-walled structures.
Accurate and efficient response sensitivities for fluid-structure interaction (FSI) simulations are important for assessing the uncertain response of coastal and off-shore structures to hydrodynamic loading. To comput...
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Accurate and efficient response sensitivities for fluid-structure interaction (FSI) simulations are important for assessing the uncertain response of coastal and off-shore structures to hydrodynamic loading. To compute gradients efficiently via the direct differentiation method (DDM) for the fully incompressible fluid formulation, approximations of the sensitivity equations are necessary, leading to inaccuracies of the computed gradients when the geometry of the fluid mesh changes rapidly between successive time steps or the fluid viscosity is nonzero. To maintain accuracy of the sensitivity computations, a quasi-incompressible fluid is assumed for the response analysis of FSI using the particle finite element method andDDMis applied to this formulation, resulting in linearized equations for the response sensitivity that are consistent with those used to compute the response. Both the response and the response sensitivity can be solved using the same unified fractional step method. FSI simulations show that although the response using the quasi-incompressible and incompressible fluid formulations is similar, only the quasi-incompressible approach gives accurate response sensitivity
In this article, a novel approach is presented for combining standard fluid-structure interaction with additional volumetric constraints to model fluid flow into and from homogenised solid domains. The proposed algori...
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In this article, a novel approach is presented for combining standard fluid-structure interaction with additional volumetric constraints to model fluid flow into and from homogenised solid domains. The proposed algorithm is particularly interesting for investigations in the field of respiratory mechanics as it enables the mutual coupling of airflow in the conducting part and local tissue deformation in the respiratory part of the lung by means of a volume constraint. In combination with a classical monolithic fluid-structure interaction approach, a comprehensive model of the human lung can be established that will be useful to gain new insights into respiratory mechanics in health and disease. To illustrate the validity and versatility of the novel approach, three numerical examples including a patient-specific lung model are presented. The proposed algorithm proves its capability of computing clinically relevant airflow distribution and tissue strain data at a level of detail that is not yet achievable, neither with current imaging techniques nor with existing computational models. Copyright (c) 2016 John Wiley & Sons, Ltd.
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