Coupled finite element/boundary element approach for fluid–structure interaction

Abstract

A new computational capability is described for calculating the sound-pressure field radiated or scattered by a harmonically excited, submerged, arbitrary, three-dimensional elastic structure. This approach, called nashua, couples a nastran finite element model of the structure with a boundary element model of the surrounding fluid. The surface fluid pressures and normal velocities are first calculated by coupling the finite element model of the structure with a discretized form of the Helmholtz surface integral equation for the exterior fluid. After generation of the fluid matrices, most of the required matrix operations are performed using the general matrix manipulation package available in nastran. Farfield radiated pressures are then calculated from the surface solution using the Helmholtz exterior integral equation. The overall capability is very general, highly automated, and requires no independent specification of the fluid mesh. An efficient, new, out-of-core block equation solver was written so that very large problems could be solved. The use of nastran as the structural analyzer permits a variety of graphical displays of results, including computer animation of the dynamic response. The overall approach is illustrated and validated using known analytic solutions for submerged spherical shells subjected to both incident pressure and uniform and nonuniform applied mechanical loads.

Application of the boundary element method to coupled fluid-structure interaction problems

“…As a first demonstration problem the boundary solution for a brass sphere sub merged in glycerine is compared with a hybrid finite element( NASTRAN)/boundary element solution [30,31]. The incident plane wave approaches along the Z-axis ( The results for the pressure p and the normal velocity vn = iwu.n are shown in Table 2.1 and Table 2.2 as magnitude-phase(#).…”

2D Structural Acoustic Analysis Using the FEM/FMBEM with Different Coupled Element Types

“…The Burton-Miller formulation (Burton, Miller, 1971) using a linear combination of CBIE (5) and HBIE (8), as given below, should give a unique solution for all frequencies:…”

“…Moreover, the Sommerfeld radiation condition at infinity is automatically satisfied for exterior acoustic problems. Making the best use of the advantages of both methods, the FEM-BEM coupling approach was developed by Everstine, Henderson (1990), and the coupled approach has been widely adopted (Chen et al, 1998;Rajakumar, Ali, 1996;Márquez et al, 2004;Fritze et al, 2005;Schneider, 2008).…”

An analysis of the response of Sooty Tern eggs to sonic boom overpressures

“…The time-of-flight of the egg white in the liquid path of 18.9 mm was 12 475 m ic e rosTc e ondr 9 This corresponds to a longitudinal ^^toto*^« 1.520 mm/microsecond. The egg yolK had a t.me-of-flight of 12.790 micro^econos ror A.l…”