BREAKDOWN OF FROZEN MOTION OF VORTICITY FIELD AND VORTICITY RECONNECTION

The perpendicular components to vorticity of the Laplacian of vorticity multiplied by the kinematic viscosity, nu-(nabla-2-omega) perpendicular-to, represents the rate of breakdown due to viscous effects of the frozen motion of vortex lines with fluid particles, whereas the parallel component, nu-(nabla-2-omega) parallel-to, represents the deviation of the stretching rates of vortex and fluid line elements. The spatial distributions of high-value regions of these two components and vorticity are compared in detail in several analytical and numerical flows. It is found that nu-(nabla-2-omega) parallel-to takes large negative values typically inside high-vorticity regions. On the other hand, nu-\(nabla-2-omega) perpendicular-to \ is large where the high-vorticity regions are interacting, which suggests that nu-(nabla-2-omega) perpendicular-to may serve as a good measure of the degree of vorticity reconnection.