AN ACOUSTIC BOUNDARY-ELEMENT METHOD USING ANALYTICAL NUMERICAL MATCHING/

Analytical/numerical matching (ANM) is a hybrid scheme combining a low -resolution global numerical solution with a high-resolution local sol ution to form a composite solution. ANM is applied to a harmonically o scillating body to calculate the radiated acoustic field and the assoc iated fluid loading. The approach utilizes overlapping smoothed dipole s, and local corrections to calculate the dipole strength distribution along the surface of the body. A smoothing length scale is introduced that is larger than the smallest physical scale, and smaller than the largest physical scale. The global low-resolution solution is calcula ted numerically using smoothed dipole solutions to the wave equation, and converges quickly. Local corrections are done with high-resolution local analytical solutions. The global numerical solution is asymptot ically matched to the local analytical solutions via a matching soluti on. The matching solution cancels the global solution in the near fiel d, and cancels the local solution in the far field. The method is very robust, offering insensitivity to node location. ANM provides high-re solution calculations from low-resolution numerics with analytical cor rections, while avoiding the usual subtleties involving singular integ ral equations, and their numerical implementation. The method is appli ed to calculate the radiated acoustic field and surface pressure of va rious flat plate configurations in two dimensions. An oscillating rigi d flat plate, a forced elastic flat plate, plane-wave diffraction, and mechanical impedance calculations are addressed. (C) 1997 Acoustical Society of America.