On Aeroacoustics of a Stagnation Flow Near a Rigid Wall

We consider propagation of disturbances in a non-uniform mean flow by high order numerical simulation. Monopole and dipole acoustic, vortical and entropy pulses are embedded in an incompressible stagnation flow, which is taken as a prototype of a non-uniform low Mach number mean flow near a rigid wall at high angle of attack. Numerical results are discussed in terms of baroclinic generation of disturbance vorticity that appear to be a key process in energy transfer between a non-uniform mean flow and a propagating disturbance. These phenomena lead to amplification of sound waves originated from an acoustic pulse. Vorticity generation governs wave radiation of a near wall entropy pulse and makes the radiated waves similar to those from a vortical dipole. Interaction of initial pulse vorticity with generated vorticity leads to various radiated wave patterns discussed here.