Tollmien–Schlichting wave

Summary

A Tollmien–Schlichting wave is an unstable travelling wave that grows in a viscous wall-bounded shear flow, such as a boundary layer or a channel flow. It is a two-dimensional eigenmode of the Orr–Sommerfeld equation that grows because of viscosity, in flows that would be stable without viscosity. Tollmien and Schlichting computed these waves around 1930, and the experiments of Schubauer and Skramstad, published in 1947, confirmed them. They are the first stage of the classical route from a laminar boundary layer to turbulence.