Numerical Simulation on Deformation and Splitting of a Noncircular Vortex Ring.

Abstract

In order to obtain information on vortical structures of noncircular jets, this paper describes the results of a vortex dynamics simulation on deformation of a pseudoelliptic vortex ring which consists of two parallel line segments of the same length connected by two semicircles of the same radius R. The cross section of the pseudoelliptic vortex ring was represented by one vortex blob to determine the evolution of its topology as a function of the aspect ratio L/(2R), where L is the length of the major axis. In a range of aspect ratio L/(2R)=2.0∼20.0, the vortex ring was found to have four fundamental patterns of deformation: pseudoperiodic axis switching; splitting into two vortex rings after axis switching; splitting into two vortex rings and their reconnection into a distorted vortex ring; splitting into three distorted vortex rings. Elimination of two antiparallel vortex blobs in close proximity was a useful means of extending the range of calculation of the deformation without having divergence of vorticity of the vortex blobs. Dynamical invariants of three-dimensional inviscid vortical motion were actually conserved within 10% of the corresponding initial values until the divergence of vorticity took place.