Development of an energy boundary element formulation for computing high-frequency sound radiation from incoherent intensity boundary conditions

An energy boundary element analysis (EBEA) formulation is presented for calculating sound radiation at high frequency from a radiator with arbitrary shape. The EBEA development presented in this paper compliments previous energy finite-element analysis (EFEA) developments for computing high-frequency vibration of structures immersed in an acoustic medium. From the EFEA solution the structural vibrational energy throughout the structure and the acoustic power radiated from each surface element in contact with the surrounding fluid are computed. The EBEA utilizes the information for the acoustic power radiated from each element of the outer surface of the structure as a boundary condition in order to compute the acoustic field in an unbound medium with no damping that surrounds the radiating structure. Since the structural vibration between different elements is considered as incoherent in the EFEA, the acoustic intensity associated with each surface element that radiates in the surrounding medium is also considered as incoherent between different elements in the EBEA formulation. The governing integral equation of EBEA is established, and a numerical solution is presented. The present method is validated by comparing EBEA results to analytical solutions and to numerical results from an axi-symmetric hp finite-element code with infinite acoustic elements suitable for structural acoustic computations. Good correlation is demonstrated for all the analyses.