A Family of Early-Time Approximations for Fluid-Structure Interaction

1980 ◽  
Vol 47 (4) ◽  
pp. 703-708 ◽  
Author(s):  
C. A. Felippa
Keyword(s):  
Plane Wave ◽  
Acoustic Impedance ◽  
High Frequency ◽  
Fluid Structure Interaction ◽  
Early Time ◽  
Surface Interaction ◽  
Structure Interaction ◽  
Differential Formulation ◽  
Impedance Characteristics ◽  
Acoustic Fluid

A hierarchical family of early-time, high-frequency asymptotic, surface interaction approximations is derived for a structure submerged in an infinite acoustic fluid. Kirchhoff’s retarded-potential integro-differential formulation is used as exact source formula. The well-known plane-wave and curved-wave approximations result as the first two members of the hierarchy. Acoustic impedance characteristics of the first four members are exhibited for several sample geometries.

Actively Silencing a Cavity by Acoustic Impedance Changes

1997 ◽  
Author(s):  
O. Lacour ◽  
D. Thenail ◽  
M. A. Galland
Keyword(s):  
Active Control ◽  
Acoustic Impedance ◽  
Fluid Structure Interaction ◽  
Central Point ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Sound Fields ◽  
Source Radiation ◽  
Absorbed Power

Abstract We attempt here the active control of enclosed sound fields via wall impedance changes. The impedance value which is the most efficient in silencing a cavity is the central point of this paper. Simulations and experiments show that the optimal impedance is not necessarily characterized by an large amount of absorbed power. Its silencing effect depends also on its ability to reduce source radiation. Experiments including fluid-structure interaction are also presented.

Nonlinear Behaviors of Three Dimensional Sloshing in the LNG Elastic Tank

2021 ◽  
Author(s):  
Zhongchang Wang ◽  
Meirong Jiang ◽  
Yang Yu
Keyword(s):  
Natural Frequency ◽  
High Frequency ◽  
Fluid Structure Interaction ◽  
Three Dimensional ◽  
Surface Elevation ◽  
Fluid Structure ◽  
Elastic Case ◽  
Structure Interaction ◽  
Elastic Tank ◽  
Sloshing Pressure

Abstract Aiming at the nonlinear sloshing in the LNG tank, a three-dimensional elastic model is established to investigate the fluid structure interaction effect. For the transient flow and the tank motion, the direct coupling method is employed to calculate the interaction between the sloshing and the bulkhead. The finite element software ADINA is adopted to do the computation. The sloshing natural frequency is verified with the results of the theoretical formula. Different wall thicknesses, filling ratios and external excitations are considered and the structure natural frequency, surface elevation and sloshing pressure are obtained. The results of the elastic case are further compared with the rigid results and the nonlinear characteristics are extracted to see the hydro-elastic effect. The sloshing natural frequencies are agreed well with the theoretical results. Due to the influence of the fluid structure interaction, the couple frequencies are obviously less than those of the empty tank. With the increase of the wall thickness, the frequencies of the empty tank and the couple frequencies all increase gradually. For the surface elevation, the thinner the bulkhead thickness is, the more the high frequency component is. The free surface is relatively flat and stable in the rigid tank but tend to be chaotic for the elastic one. Due to the fluid structure interaction, the sloshing pressure of the elastic case presents obvious high-frequency fluctuation and the sloshing pressure in the elastic tank is smaller than that in the rigid tank. This model clearly shows the valuable ability to solve the three dimensional sloshing in the elastic tank.

A Coupled FEM/BEM for Fluid-Structure Interaction Using Ritz Vectors and Eigenvectors

1993 ◽  
Vol 115 (2) ◽  
pp. 152-158 ◽  
Author(s):  
A. F. Seybert ◽  
T. W. Wu ◽  
W. L. Li
Keyword(s):  
Numerical Solutions ◽  
Fluid Structure Interaction ◽  
Normal Vector ◽  
Normal Velocity ◽  
Error Norm ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Acoustic Equations ◽  
Ritz Vectors ◽  
Acoustic Fluid

In this paper, the finite element (FEM) and the boundary element method (BEM) are combined together to solve a class of fluid-structure interaction problems. The FEM is used to model the elastic structure and the BEM is used to model the acoustic fluid. Quadratic isoparametric elements are used in both the FEM and BEM models. Continuity conditions of pressure and normal velocity are enforced at the fluid-structure interface on which the normal vector is not required to be uniquely defined. An enhanced CHIEF formulation is adopted to overcome the nonuniqueness difficulty at critical frequencies. To reduce the dimension of the coupled structural acoustic equations, the structural displacement is approximated by a linear combination of either Ritz vectors or eigenvectors. An error norm and a participation factor are defined so that it is possible to evaluate the accuracy of a solution and to omit vectors with small participation factors. Example problems are solved to examine the accuracy of the numerical solutions and to compare the efficiency of the Ritz vector and eigenvector syntheses.

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