Effects of Compression and Expansion on Turbulence Intensity in Supersonic Boundary Layers

Abstract

The effects of bulk expansion and compression on turbulence levels in supersonic boundary layers were predicted using the law of angular momentum conservation. For the compression case the present analysis predicted the amplification of turbulence level quite well when the effect of extra strain rate caused by the streamline curvature is small, where it was estimated that 90-95% of the increase in the turbulence level is caused by the bulk compression. When extra strain rate effects are present, however, the contribution of the bulk compression on the total turbulence level was reduced to about 85-90%. The predicted general trend of turbulence amplification with increasing flow-turning angle, which seems to be closely related to the linear increase in the mean density, agrees well with that of other researchers. For the expansion case, however, a quantitative comparison was challenging because the available experimental data were taken too close to the end of the perturbation region, thus not showing the relaxation behavior