An experimental study has been made of air flow over a rearward facing step where the free-stream velocity has been perturbed by a sinusoidal fluctuation of 1 Hz. Velocities have been measured using a laser-Doppler anemometer employing a gated photon correlation signal detection system. This allows mean velocities and fluctuating components to be measured at different phase positions in the cycle. It is shown that the stability of the separated flow region behind the step is strongly perturbed by the free-stream oscillations and that the position of reattachment of the turbulent boundary layer is dependent on the phase of the free-stream velocity. Shedding of the vortex occurs when the retardation of the free-stream velocity is a maximum. © 1980 American Institute of Physics.
|Number of pages||6|
|Journal||Physics of Fluids|
|Publication status||Published - 1980|