Kelvin–Helmholtz instability

Summary

The Kelvin–Helmholtz instability is the instability of a shear layer, where two layers of fluid slide past each other. Small waves on the interface grow and roll up into a row of vortices. The simplest model has two uniform streams separated by a sharp interface. In it every wavelength is unstable unless gravity or surface tension holds the long or short waves back. It is a basic mechanism of hydrodynamic stability and of mixing in the atmosphere, the ocean and astrophysical flows.