ON NOISE EMISSION DURING COAXIAL VORTEX RING COLLISION

Vortex simulations of coaxial vortex ring collisions are used to predi ct the impact of 3D vortex motion on far-field noise radiation. It is shown that nonlinear growth of azimuthal bending waves on rings with m oderate core size to radius ratio leads to small departures from axisy mmetric predictions. Meanwhile, the evolution of traveling waves on sl ender vortices results in large increase in acoustic pressure levels. It is suggested that the observed differences are linked to small nonl inear time-scales which characterize slender cores, and to convolution s in pressure predictions which naturally minimize the impact of high wavenumber modes.