SIMULATIONS OF THE FORMATION OF AN AXISYMMETRICAL VORTEX RING

In this paper we present the results from numerical calculations, base d upon the Navier-Stokes equations at relatively high Reynolds number, of the formation of a vortex ring when fluid is ejected from a circul ar tube. Our results are compared with the experiments of Didden (1979 ), and the inviscid flow calculations of Nitsche & Krasny (1994). Reas onable agreement is achieved except for the rate of shedding of circul ation during the initial stages of ring formation. The theoretically p redicted rate of shedding is substantially higher than that predicted by Didden. By contrast the inviscid theory predicts an anomalously hig h rate of initial shedding. We offer explanations for both of these ap parent discrepancies.