Effect of free-stream turbulence on turbulent properties of a separation-reattachment flow

A study of the effect of free-stream turbulence on the turbulent structure of a separation bubble formed at the leading edge of a blunt plate with right-angled corners is presented. The free-stream turbulence was introduced by a thin circular rod placed upstream of the plate along its stagnation streamline. This paper is a sequel to previous papers by Kiya and Sasaki (1983) and Kiya et al. (1984), in which time-averaged properties of the separation bubble are determined in terms of the turbulence intensity at a reference point near an edge of the plate. The longitudinal and spanwise integral length scales of vortices in the separation bubble are given as functions of the free-stream turbulence intensity. The cross correlations between the surface-pressure and velocity fluctuations suggested that large-scale vortices are similar in shape independently of the free-stream turbulence intensity. Moreover, the maximum rms surface pressure was estimated in terms of the longitudinal gradient of the time-mean surface-pressure profile and the longitudinal length scale of vortices in the reattaching zone.