Effects of compression and expansion on turbulence intensity in supersonicboundary layers

The effects of bulk expansion and compression on turbulence levels in super sonic boundary layers were predicted using the law of angular momentum cons ervation. For the compression case the present analysis predicted the ampli fication of turbulence level quite well when the effect of extra strain rat e 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 compre ssion. When extra strain rate effects are present, however, the contributio n of the bulk compression on the total turbulence level was reduced to abou t 85-90%. The predicted general trend of turbulence amplification with incr easing flow-turning angle, which seems to be closely related to the linear increase in the mean density agrees well with that of other researchers. Fo r the expansion case, however, a quantitative comparison was challenging be cause the available experimental data were taken too close to the end of th e perturbation region, thus not showing the relaxation behavior. In both co mpression and expansion flows the bulk dilatation was found to be the domin ant factor responsible for the changed turbulence intensity.