Some recent attempts at predicting turbulent two- dimensional recirculating flows have concentrated on modelling the turbulent energy equations used in the finite difference analysis methods of solutions of the elliptic partial differential equations governing these flows. These attempts have to some extent been restricted by the lack of experimental studies of the high turbulence intensities found in separated flows. The improvement of the pulsed hot-wire anemometer and the laser Doppler anemometer have made possible such studies and this paper describes an investigation using the laser Doppler anemometer in a separated flow situation. Results are given of an experimental study of the plane turbulent separated flow of water over a double backward facing step of duct height ratio 3:1. Time mean streamwise, transverse and cross-stream components of velocity are reported, together with the turbulent velocity fluctuations. The measurements were made using a laser Doppler anemometer operating in the differential Doppler mode with forward scattering. The problem of high turbulence intensity and instantaneous flow reversals was overcome by frequency shifting of the incident laser light beams using a pair of Bragg cells. Substantial changes in flow patterns were detected together with turbulence intensities based on local streamwise velocity of up to 100% were recorded in the recirculating zones. Transverse turbulence intensities were in general about half that of the streamwise components, with cross-stream intensities an order of magnitude lower again.
Smyth, R., "Experimental Study of Turbulence in Plane Separated Flows" (1975). Symposia on Turbulence in Liquids. 29.
4th Biennial Symposium on Turbulence in Liquids (1975: Sep., Rolla, MO)
Chemical and Biochemical Engineering
Article - Conference proceedings
Separated Turbulent Flows
© 1975 University of Missouri--Rolla, All rights reserved.