INSTABILITY OF STRAINED VORTEX LAYERS AND VORTEX TUBE FORMATION IN HOMOGENEOUS TURBULENCE

A modulational perturbation analysis is presented which shows that whe n a strained vortex layer becomes unstable, vorticity concentrates int o steady tubular structures with finite amplitude, in quantitative agr eement with the numerical simulations of Lin and Corcos (1984). Elabor ated three-dimensional visualizations suggest that this process, due t o a combination of compression and self-induced rotation of the layer, is at the origin of intense and long-lived vortex tubes observed in d irect numerical simulations of homogeneous turbulence.