Abstract:
Boundary layer developments have been measured for the flow downstream of an expansion corner when the boundary layer is disturbed by a shock wave striking the surface near the corner. It is found that most velocity profiles quickly relax to a near-equilibrium state in about 8 to 16 boundary-layer thicknesses with the actual distance depending on the shock strength. However, this equilibrium state is not the same as that in a flat-plate boundary layer at the same Mach number and Reynolds number. In spite of this, the velocity profiles downstream of the interaction collapse onto the low-speed law of the wall when plotted in terms of Van Driest's transformed velocity coordinates. The boundary layer developments are in fair agreement with the predictions from an eddy-viscosity model when the incident shock is weak. However, the agreement was much improved if the calculation was started from the first measured profile after the shock interaction, and the prediction from the eddy-viscosity model was further improved if an exponential lag equation was used to account for the transport properties of the turbulence.
