The Journal of the Acoustical Society of America · 1990 · 269 citations · 0 references
EngineeringComputational EngineeringPhysicsAcousticsFinite Element AnalysisFluid DynamicsBoundary Element MethodsFinite Element FormulationNumerical AcousticsShell AnalysisStructural AcousticsStructural Finite Element AnalysisBoundary Element AnalysisBoundary Element CouplingBoundary Element Methods For Acoustic RadiationBoundary Element Methods In AcousticsDynamic ResponseDynamic Response ValidationFinite Element ModelingHelmholtz Equation
The method introduces a new computational capability for predicting the sound‑pressure field radiated or scattered by a harmonically excited, submerged, arbitrary, three‑dimensional elastic structure. It couples a Nastran finite‑element model of the structure with a boundary‑element model of the surrounding fluid, solves the Helmholtz surface integral equation using Nastran’s matrix operations, and employs an efficient out‑of‑core block solver to handle very large problems. The resulting approach is highly general, fully automated, requires no independent fluid mesh, and has been validated against analytic solutions for submerged spherical shells, enabling graphical displays and animation of the dynamic response.
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.