Zigzag instability of vortex arrays in stratified and rotating fluids
Seminar Room 1, Newton Institute
We investigate the three-dimensional stability of columnar vertical vortex arrays (Karman street, double symmetric row of vortices) in a stratified and rotating fluid by means of an asymptotic theory for long-vertical wavelength and well-separated vortices. It is found that both the Karman street and the double symmetric row are unstable to the zigzag instability when the fluid is stratified independently of the background rotation. The zigzag instability bends the vortices with almost no internal deformation and ultimately slices the flow into horizontal layers. The results are in excellent agreement with direct numerical stability analyses. They may explain the formation of layers commonly observed in stratified flows.