Merging of non-symmetric Burgers vortices

The merging of two Burgers vortices in an irrotational background straining flow at high Reynolds number is studied. Both axisymmetric and biaxial strain fields are considered. The merging events produce fine scale spiral vortex structures. For biaxial strain, a cat’s-eye streamline pattern emerges and vorticity is transported away by the background strain. For intermediate strain ratios, the onset of vortex merging is delayed and the resulting vorticity contours are distorted compared to the axisymmetric case. The merging is suppressed for sufficiently large strain ratios.