Simulations and analysis of the coupling process of compressible vortex pairs: Free evolution and shock induced coupling

摘要

In the present paper the dynamics of the coupling process of compressible vortex pairs is analyzed by means of extensive numerical simulations. The objective of the study is to determine the effects of the initial vortex spatial structure and of the compressibility. Different vortex structures have been considered and their influence on the vorticity dynamics has been assessed. In the case of free evolution, the numerical simulations show that two vortices in close contact evolve toward a vortex dipole; however, the structure of the resulting dipole depends upon the initial inner core structure and on the vortex intensity. In the presence of shock wave-vortex pair interaction the coupling process depends upon the strength of the shock and the type of pair. In the case of a colliding pair, the process obeys either a two- or a three-stage mechanism depending upon the shock strength, and nonlinear couples form regardless of the initial vortex Mach number. If the interacting shock is strong, the vortex pair experiences a three-stage evolution, whereby the intermediate stage is characterized by the occurrence of a transient nonsymmetric couple. In the case of passing pair, the coupling mechanism proceeds in four stages. In particular, we observe the formation of satellite vortices, whose interaction with the primary vortex during the transient gives rise to the formation of a nonsymmetric dipole and a subsequent temporary tripole due to the feeding of shear produced vorticity. The final stage of the interaction is characterized by the formation of a nonlinear dipole. (C) 2001 American Institute of Physics. [References: 18]