Numerical study of fluid loading approximations for submerged spherical shells using finite, infinite and boundary element methods

Numerical studies were conducted to compare acoustic fluid loading approximations for submerged spherical shells. Rigid and empty elastic shells submerged in a heavy acoustic fluid and subjected to harmonic excitation were considered. Solutions using boundary elements, infinite elements, and analytical approximations were compared, with special attention to modeling the near-field fluid beneath the infinite elements. In this case, the near-field fluid is typically modeled using fluid finite elements with frequency dependent mesh refinement and radial extent. The spherical shell is modeled in the same manner using shell finite elements for both boundary and infinite element solutions in order to provide a direct comparison of the fluid loading approximations. Convergence studies involving the near-field fluid were performed with emphasis on the effects of meshing parameters, including refinement, mesh grading, and polynomial order of the radial basis functions for p-version fluid finite elements. Results of interest include comparisons of the submerged structural response, focusing on the reactive and resistance parts of the fluid impedance.