fluid-structure interaction (FSI) is a phenomenon caused by mutual interference between structures and the surrounding flow. Controlling FSI is important because FSI causes undesired vibration and it often affects the...
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fluid-structure interaction (FSI) is a phenomenon caused by mutual interference between structures and the surrounding flow. Controlling FSI is important because FSI causes undesired vibration and it often affects the safety and lifetime of structures. Piezoelectric materials have excellent electromechanical properties to suppress vibration. As such, piezoelectric sensors and actuators are often used for reducing not only mechanical vibration but also FSI induced vibration. A number of studies have examined active control of FSI using piezoelectric materials. In the study of the control of FSI, numerical simulations are effective because they are proper for parametric studies and reduce the need for experiments. Although a number of numerical studies examined the control of FSI using piezoelectric materials, in these studies, detailed fluid analyses were not performed and the fluid force was modeled as a simple function. As such, the existing method cannot treat complicated FSI problems. Therefore, we herein propose a general-purpose system that conducts detailed electrostatic, structural, and fluid analyses and considers an active control algorithm. We design a structure-fluid-electrostatic interaction analysis system considering active control by inserting electrostatic analysis into FSI analysis solved by the partitioned iterative method and integrating the active control algorithm. In the present study, we verify the proposed system in three ways. First, while varying the material properties of the fluid, we analyze the motion of a bimorph piezoelectric actuator in a non-flowing fluid and compare the results with those of a previous study that did not take the fluid into consideration. Second, we reproduce vortex-induced vibration (VIV), which is an FSI phenomenon using the proposed system. Third, we confirm that the active control algorithm is implemented correctly by solving the suppression of VIV with the velocity feedback control. Based on these verification
The customary subiteration method for solving fluid-structure-interaction problems exhibits several deficiencies, viz., only conditional stability, potential convergence difficulties due to non-normality-induced diver...
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The customary subiteration method for solving fluid-structure-interaction problems exhibits several deficiencies, viz., only conditional stability, potential convergence difficulties due to non-normality-induced divergence, and the inability to reuse information from previously solved similar problems. To overcome these deficiencies, a novel solution method is considered, in which subiteration is used as a preconditioner to GMRES. This paper treats the linear-algebra aspects of the subiteration method, and of the subiteration-preconditioned GMRES method, on the basis of properties of the error-amplification matrix for the aggregated fluid-structure system. An analysis of the error-amplification matrix of subiteration establishes that subiteration condenses errors into a low-dimensional subspace which can be associated with the interface degrees-of-freedom. Therefore, the GMRES acceleration of subiteration can be confined to the interface degrees-of-freedom. The error-amplification analysis provides a clear explanation of the relation between the local GMRES acceleration (i.e., on the interface degrees-of-freedom), and the global error-amplification properties (i.e., for the aggregated system). Moreover, we show that the subiteration iterates span a Krylov space corresponding to a preconditioned aggregated system. We then address the implications of the non-normality of the subiteration preconditioner for the convergence of GMRES. The subiteration-preconditioned GMRES method enables the optional reuse of Krylov vectors in subsequent invocations of GMRES, which can substantially enhance the efficiency of the method. To assess the potential and the limitations of the reuse option, we analyse the error-amplification matrix of the GMRES method with reuse. Furthermore, we establish that the GMRES acceleration on the interface degrees-of-freedom generates an approximation to the Schur complement for the aggregated system. The GMRES acceleration and the reuse of Krylov vect
fluid-structure interaction (FSI) can be simulated in a monolithic way by solving the flow and structural equations simultaneously and in a partitioned way with separate solvers for the flow equations and the structur...
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fluid-structure interaction (FSI) can be simulated in a monolithic way by solving the flow and structural equations simultaneously and in a partitioned way with separate solvers for the flow equations and the structural equations. A partitioned quasi-Newton technique which solves the coupled problem through nonlinear equations corresponding to the interface position is presented and its performance is compared with a monolithic Newton algorithm. Various structural configurations with an incompressible fluid are solved, and the ratio of the time for the partitioned simulation, when convergence is reached, to the time for the monolithic simulation is found to be between 1/2 and 4. However. in this comparison of the partitioned and monolithic simulations, the flow and structural equations have been solved with a direct sparse solver in full Newton-Raphson iterations, only relatively small problems have been solved and this ratio would likely change if large industrial problems were considered or if other solution strategies were used. (C) 2008 Elsevier Ltd. All rights reserved.
A novel analytical method is presented in this paper for evaluating the propagation characteristics of structure-borne sound in a T-joint, the web plate of which is in contact with heavy fluid. Firstly, based on the d...
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A novel analytical method is presented in this paper for evaluating the propagation characteristics of structure-borne sound in a T-joint, the web plate of which is in contact with heavy fluid. Firstly, based on the dynamics of fluid-structure interaction, a mathematical model that considers the effect of fluid is established for the T-joint, which is equipped with a dynamic vibration absorber. The waves in the T-joint structure are described by the dynamical equation of thin plates, while the motion of fluid is described by the Helmholtz equation in the ideal acoustic medium. For the convenience of mathematics, the semi-infinite fluid domain is extended virtually into the infinite space. The Fourier transform method is utilized to obtain analytical solutions with high precision. Several examples are given to analyse the characteristics of the coupled transmission of bending and longitudinal waves in the T-joint. Comparisons are made with the results for the no-fluid case. The effects of the mass and frequency parameters of the dynamic vibration absorber on the inhibition of longitudinal wave transmission are also investigated. It is found that the existence of the heavy fluid has a significant influence on the propagation of bending waves in the T-joint. The dynamic absorber can inhibit the longitudinal waves in the web plate of the T-joint, while it has no effect on the bending waves.
In order to investigate the effect of density ratio of fluid and solid on the convergence behavior of partitioned FSI algorithm, three strong-coupling partitioned algorithms (fixed-point method with a constant under-r...
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In order to investigate the effect of density ratio of fluid and solid on the convergence behavior of partitioned FSI algorithm, three strong-coupling partitioned algorithms (fixed-point method with a constant under-relaxation parameter, Aitken's method and Quasi-Newton inverse least squares (QN-ILS) method) have been considered in the context of finite element method. We have employed the incompressible Navier-Stokes equations for a Newtonian fluid domain and the total Lagrangian formulation for a nonlinear motion of solid domain. Linear-elastic (hyper-elastic) model has been employed for solid material with small (large) deformation. A pulsatile inlet-flow interacting with a 2D circular channel of linear-elastic material and a pressure wave propagation in a 3D flexible vessel have been simulated. Both linear-elastic and hyper-elastic (Mooney-Rivlin) models have been adopted for the 3D flexible vessel. From the present numerical experiments, we have found that QN-ILS outperforms the others leading to a robust convergence regardless of the density ratio for both linear-elastic and hyper-elastic models. On the other hand, the performances of the fixed-point method with a constant under-relaxation parameter and the Aitken's method depend strongly on the density ratio, relaxation parameter selected for coupling iteration, and degree of deformation. Although the QN-ILS of this work is still slower than a monolithic method for serial computation, it has an advantage of easier parallelization due to the modularity of the partitioned FSI algorithm. (C) 2020 Published by Elsevier Ltd.
In this work we deal with the numerical solution of the fluid-structure interaction problem arising in the haemodynamic environment. In particular, we consider BDF and Newmark time discretization schemes, and we study...
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In this work we deal with the numerical solution of the fluid-structure interaction problem arising in the haemodynamic environment. In particular, we consider BDF and Newmark time discretization schemes, and we study different methods for the treatment of the fluid-structure interface position, focusing on partitioned algorithms for the prescription of the physical continuity conditions at the fluid-structure interface. We consider semi-implicit and implicit algorithms, and a new family of hybrid methods. We study numerically the performance and the accuracy of these schemes, highlighting the best solutions for haemodynamic applications. We also study numerically their convergence properties with respect to time discretization, by introducing an analytical test case. (C) 2013 Elsevier Ltd. All rights reserved.
In this work we address the numerical solution of large scale fluid-structure interaction problems when nonconforming grids and/or nonconforming finite elements discretizations are used at the interface separating the...
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In this work we address the numerical solution of large scale fluid-structure interaction problems when nonconforming grids and/or nonconforming finite elements discretizations are used at the interface separating the fluid and structure physical domains. To deal with nonconforming fluid-structure discretizations we use the INTERNODES method (INTER- polation for NOnconforming DEcompositionS) formerly introduced in [6] for the solution of elliptic PDEs on nonconforming domain decomposition. To cope with the high com- putational complexity of the three dimensional FSI problem obtained after spatial and temporal discretization, we use the block parallel preconditioner FaCSI [7]. A numerical investigation of the accuracy properties of INTERNODES applied to the nonconforming FSI problem is carried out for the simulation of the pressure wave propagation in a straight elastic cylinder. Finally, we study the scalability performance of the FaCSI precondition- er in the nonconforming case by solving a large-scale nonconforming FSI problem in a patient-specific arterial bypass.
Shell and tube heat exchanger is an important part of industrial heating and cooling system. Because of the harsh operating conditions, and its complex fin and baffle structure with numerous holes, it is a great chall...
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Shell and tube heat exchanger is an important part of industrial heating and cooling system. Because of the harsh operating conditions, and its complex fin and baffle structure with numerous holes, it is a great challenge for engineers to design and evaluate the baffle structure on the premise of ensuring the comprehensive performance. This paper aims to provide a method to optimize the baffle structure of torsional flow heat exchanger by comprehensively considering thermal, hydraulic, and mechanical properties. Based on fluid-structure interaction method, response surface methodology was applied to improve the structure configurations of torsional flow heat exchanger. The results show that the effects of various input parameters on objectives are related to each other, and the baffle width and inclination angle have a more obvious impact on heat exchanger. The tradeoff analysis is carried out for the optimization objectives, the candidate points obtained by optimization reveal that the fluid comprehensive performance of the optimal structure is increased by 10.99%, and the maximum equivalent stress is reduced by 8.74%. The research results offer theoretical guidance for the equipment maintenance and structural design of torsional flow heat exchanger.
Laboratory-scale dynamic experiments are performed in order to explore the one-dimensional response of unsupported rigid plates to loading by exponentially decaying planar shock waves in deep water. Experiments are co...
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Laboratory-scale dynamic experiments are performed in order to explore the one-dimensional response of unsupported rigid plates to loading by exponentially decaying planar shock waves in deep water. Experiments are conducted in a transparent shock tube allowing measurements of plate motion and imparted impulse, as well as observation of cavitation in water, including motion of breaking fronts and closing fronts. Loading of both air-backed and water-backed rigid plates is examined, and the sensitivity of plate motion and imparted impulse to the structural mass and to the initial hydrostatic pressure in the water is measured. Experiments also serve to validate recently developed theoretical models, whose predictions are found to be in agreement with measurements.
Continuum Sensitivity Equation (CSE) methods for deriving and computing derivatives with respect to shape design variables are developed in two forms and compared in their application to fluid-structure interaction (F...
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Continuum Sensitivity Equation (CSE) methods for deriving and computing derivatives with respect to shape design variables are developed in two forms and compared in their application to fluid-structure interaction (FSI) problems. The local derivative form poses the CSEs in terms of the partial derivatives of the state variables with respect to shape parameters, while the CSEs in total derivative form are posed in terms of the total derivative, also known as the material or substantial derivative. In the literature CSEs are often posed in local form for fluids and total form for solids. The two forms are compared here for the purpose of applying a single form to both fluid and structure domains. The local form, also known as the boundary velocity method, requires design velocity only at the boundaries and interfaces of the domains to pose the CSEs. In contrast, the total form, also known as the domain velocity method, requires the design velocity in the whole domain. The local form requires higher-order spatial derivatives of the analysis solution than the total form, which affects the accuracy of its results. Higher order p-elements are shown to be a remedy to the inaccuracy of local form CSE seen in the literature for finite element solutions. The practicality, accuracy, and efficiency of these two CSE forms are compared based on the implementation and computed derivatives for three examples: a linear Timoshenko beam subject to a tip force, fluid flow around an airfoil, and an airfoil attached to a nonlinear joined beam subject to a gust load. Published by Elsevier Ltd.
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