| dc.description |
Experiments were performed to investigate the supersonic flow of a turbulent boundary layer over a number of compression-corner models. Upstream of each corner, the free-stream Mach number was 2.9 and the incoming boundary layer was typical of a two-dimensional, zero-pressure-gradient, high-Reynolds-number flow. Three different corner angles were used, namely 8°, 16° and 20°, and at the highest angle the interaction was strong enough to cause separation. Each flow was investigated using normal and inclined hot wires, and measurements of the longitudinal mass-flux fluctuations and the mass-weighted turbulent shear stress are presented. The behaviour of the kinematic and Reynolds stresses, deduced from the mass-weighted quantities by applying Morkovinʼs ‘strong Reynolds analogy’, is also considered. In all three flow cases, the interaction dramatically amplifies the turbulent stresses, and the amplification increases with increasing turning angle. Different stress components are amplified by different amounts, however, and the structure parameter $-\overline{u^{\prime}v^{\prime}}/\overline{u^{\prime 2}}$ changes significantly through the interaction. Perhaps more importantly, the nature of these changes depends on the strength of the interaction. This result is rather unexpected, and it is believed to be due mainly to the unsteadiness of the shock system. It is suggested that the apparently random motion of the shock system affects the normal stresses more than the shearing stresses, and, since the unsteadiness increases with corner angle, the effect on the turbulence structure also becomes more pronounced. |
