Hypersonic boundary-layer separation and the base flow problem.

Abstract

A detailed analytical investigation of the expansion and of a hypersonic boundary layer at the shoulder of a blunt-based body is presented. The expansion of the body boundary layer is assumed to be inviscid, and numerical results are obtained with a rotational characteristics calculation. A at constant (base) pressure provides the required boundary condition downstream of the shoulder. With the base pressure given by a simple model of the complete base flow, it is possible to calculate the entire vortical flow above this in detail. It is found that both the constant pressure and the nearby dividing streamline are highly curved, concave outward, causing the rear stagnation point to be located quite close to the base. The formation of the separation shock wave is shown, and its shape and inclination angle are discussed. At high Mach numbers, the expansionseparation process dominates the entire base flow, producing a nonparallel vortical region that extends into the far wake. Finally, an approximate solution of the viscous free shear layer is derived. The temperature distribution behind a wedge is calculated and compared to experimental data.