Aeroacoustics of a stagnation flow near a rigid wall

Propagation of disturbances in a nonuniform mean flow is investigated by hi gh-order numerical simulation for various initial conditions. Monopole and dipole acoustic, vortical and entropy pulses are embedded in an incompressi ble stagnation flow, which is taken as a prototype of a nonuniform low Mach number mean flow near a rigid wall at high angle of attack. Numerical resu lts are discussed in terms of baroclinic generation of disturbance vorticit y that appear to be a key process in energy transfer between a nonuniform m ean flow and a propagating disturbance. These phenomena lead to amplificati on of sound waves originated from an acoustic pulse. Vorticity generation g overns wave radiation of a near-wall entropy pulse and makes the radiated w aves similar to those from a vortical dipole. Interaction of initial pulse vorticity with generated vorticity leads to various radiated wave patterns discussed here. (C) 2000 American Institute of Physics. [S1070- 6631(00)508 10-1].