Turbulent Separated and Reattached Flow Over a Curved Surface

Abstract

An experimental investigation of two-dimensional separated and reattached turbulent flow has been carried out in a wind tunnel. The test surface consisted of a five to one, length to height, polynomial curve having zero slope and curvature at both ends. Data were taken at reference speeds of 9.1 m/s (30 f/s) and 15.2 m/s (50 f/s). Surface mean pressure distributions and fluctuations were measured. The pressure coefficient was found to agree with a potential flow prediction up to 40 percent of the chord. Significant pressure fluctuations were observed well upstream of separation. Velocity profiles, profile scaling parameters, and integral thickness variations were also measured. Intermittency measurements, i.e., the fraction of time that reversed flow existed at a place, showed that both the separation point and reattachment point wandered over about 30 percent of the chord. Nowhere in the separated region was the intermittency found to be 100 percent. Wall shear stress distributions were measured from upstream of separation to downstream of reattachment.