ACCURACY OF PITOT-PRESSURE RAKES FOR TURBULENT BOUNDARY-LAYER MEASUREMENTS IN SUPERSONIC FLOW

摘要

Boundary-layer profiles from three conventional pitot-pressure rakes and a new probeless rake are compared with those from a single traversing probe in a supersonic turbulent boundary layer on the wall of a wind tunnel. Measurements were made at Mach numbers from 2.4 to 3.4 and at momentum-thickness Reynolds numbers from 26,000 to 75,000. The boundary-layer thickness was approximately 6 inches and the rake heights were 5, 8, and 12 inches with different probe size and spacing.nThe pitot pressures from both the conventional rakes and the probeless rake agree with the single traversing-probe pressure within 2 percent of the edge pitot pressure. The resulting errors in Mach number and velocity ratios are less than 2 percent;momentum and displacement thickness errors are less then 4 percent. These errors are not excessive and indicate that multiple-probe and probeless rakes can be used in measuring turbulent boundary layer.nThe low error of the probeless rake indicates that this type of configuration might have useful application at high temperatures where conventional rake probes might warp or fail.