Free-stream turbulence effects on a separation bubble

Abstract

Effects of free-stream turbulence on a separation bubble formed along a side of a blunt plate with right-angled corners are studied. The free-stream turbulence was generated by a thin circular rod which was placed at a certain distance upstream of the plate along its stagnation streamline. Various characteristic parameters of the separation bubble such as the bubble length, the integral length scale of large-scale vortices, the maximum pressure difference in the bubble, a few characteristics lengths of the time-mean pressure profile etc. are fairly well correlated with the turbulence intensity just outside the separated shear layer near the edge. The turbulence length scale there was a fairly unique function of the turbulence intensity. Statistical properties of the fluctuating surface pressure are also studied and used to demonstrate the large-scale vortices in the reattaching zone. The maximum r.m.s. surface pressure was found to be estimated in terms of the longitudinal gradient of the time-mean pressure and the length scale of vortices in the reattaching zone.