Transonic Shock Wave - Boundary Layer Interactions.

Abstract

Abstract : A series of 2D experiments was performed in a large-scale Ludwieg tube to investigate the interactions of a normal shock with a turbulent boundary layer at unit Reynolds numbers 14.8 million and 29.5 million/m and Mach numbers 1.43 and 1.60. In addition, the effects of a diverging flow field downstream of the shock, such as that which might be encountered on an airfoil, were explored by testing with a shock holder having a perforated top wall. The latter experiments were performed at the two Reynolds number values of 9 million and 35 million. Results show that unit Re variations affected the interacting flow only by changing the boundary layer entering the interaction. The surface pressure distribution normalized by the thickness of the incoming boundary layer, which was measured in each experiment, describes an interaction independent of unit Re. In contrast, the interaction flow field was found to be very dependent on Mach number and on constrainment of the subsonic region. In fact, shock configuration, surface pressure, skin friction and velocity profiles were found much more sensitive to these parameters than to the Reynolds number, which was investigated in earlier studies. the bifurcation height and the length of separated flow increased with increasing M. Both quantities responded dramatically to the moderate but sustained flow deflections imposed by the perforated shock holders. The initial rise in surface pressure was found to correlate directly with the height of the bifurcated shock structure.