ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

5aPA15. Simulation of wave propagation through an inhomogeneous turbulent medium with the aid of an integral formulation.

Hirobumi Kaneko

130C Olde Derby Rd., Norwood, MA 02062

A propagation simulation algorithm is described whereby, at the beginning of step n, the pressure associated with a progressive wave is specified as a function of time and lateral position along a planar surface, x=x[sub n]. The algorithm for step n yields the pressure as a function of time and lateral position at x=x[sub n+1]. The basic mathematical formulation employs an integral equation that predicts the waveforms at arbitrary positions to the right of the first surface. The medium between the point and the surface, x=x[sub n], is turbulent. The integral over the surface involves the Green's function for a point source in the actual medium. Although the exact Green's function is extremely difficult to compute, it is argued that a good approximation for moderate step sizes, |x[sub n-1]-x[sub n]|, results if the Green's function is taken to be that which results from a ray-acoustics approximation. Moreover, because the first caustic for a point source Green's function is not encountered for a distance considerably longer than the distance between successive caustics for a nominally parallel group of rays within a ray tube, the difficulties of explicitly taking caustics into account is circumvented with this algorithm.