Numerical study of wave propagation in a nonuniform compressible flow

The propagation of acoustic waves originating from cylindrical and spherical pulses in a nonuniform mean flow, and in the presence of a reflecting wall, is investigated by solving linearized Euler equations in terms of disturbances using high-order compact approximation of spatial derivatives. The two-dimensional and three-dimensional stagnation flows and a flow around a cylinder are taken as prototypes of real-world flows with strong gradients of mean pressure and velocity. The intensity and directivity of acoustic wave patterns appear to be quite different from the benchmark solutions obtained in a static environment for the same geometry. The physical reasons for amplification of sound are discussed in terms of redistribution of acoustic energy and its potential and kinetic components. The role of acoustic energy exchange with the mean flow is investigated. Compressibility of the background mean flow is taken into account and its effect on amplification of acoustic pressure is discussed. (C) 2002 American Institute of Physics.