On Instability of Acoustic Waves Propagating in Stratified Vortical Flows

The propagation of sound waves in a finite vortex is investigated by numerically solving the linearized Euler equations in two dimensions. Two types of vortices are considered: homentropic, when the entropy is uniformly distributed in space, and non-homentropic, or entropy stratified, when it is distributed non-uniformly. In the latter case, the results reveal instability of the perturbation field, which is caused by entropy-rotational waves excited in the vortex region by incident sound waves.