Unsteady turbulent boundary layers - Some effects of abrupt free-stream velocity changes

The response of a turbulent boundary layer to abrupt changes in free-stream velocity is studied. Streamwise velocity measurements are examined during the abrupt events and after them, as the flow relaxes to its equilibrium condition. The measured velocity field is found to be in good agreement with the analytic solution of the Stokes equation for boundary conditions describing abrupt changes. While the flow recovers to its equilibrium state, changes in integral, boundary-layer parameters scale on the local free-stream time of flight.