This animation shows the generation and lift-off of vortices due to an isolated hemispherical roughness element in the presence of an oscillatory boundary layer.
The external flow is imposed by a sinusoidally varying body force. The Reynolds number, based upon peak far-field velocity, hemisphere radius, and kinematic viscosity, is Re=200. The period of oscillation is 40 convective time units (40 R/U).
Last update: January 23, 1999 (pff)