Experimental study of turbulence in plane separated flows

An experimental study is made of high turbulence intensities found in separated flow situations. Results are given for the plane turbulent separated flow of water over a double backward facing step of duct height ratio three to one. The investigation used the laser Doppler anemometer to measure mean streamwise, transverse, and cross-stream components of velocity; the problem of high turbulence intensity and instantaneous flow reversals was overcome by frequency shifts in the incident laser beam. Significant changes in flow patterns were recorded, as well as turbulence intensities based on the local streamwise velocities of up to 100%; transverse turbulence intensities were about half that of streamwise components, and cross-stream intensities were an order of magnitude lower.