Experimental Investigation of Skin Friction Drag and Heat Transfer on the Surfaces With Concavities in Compressible Fluid Flow

Abstract

This experimental study has been performed to investigate the surface heat transfer enhancement in compressible fluid flow by using hemispherical concavities (dimples). The experiments were carrying out in supersonic wind-tunnel with free-stream Mach number 2,8. Using the IR-imager the temperature fields of the testing plates were obtained at any time of experiments. The studying of these fields at unsteady conditions allowed to obtain the area-averaged heat transfer coefficient. The skin friction drag of the test plates was found by direct weight measurement with using a “smoothing element”. The skin friction drag and heat transfer were measured simultaneously (at the same conditions) in each experiment. The plate with dimples with ratio of dimple depth to dimple print diameter 0,14 was investigated. It was shown that the tested surface with concavities (vortex generation relief) intensified the heat transfer and decreased the recovery factor in supersonic flow. The ratio of the heat transfer enhancement to the skin friction drag increasing for the dimpled surface in compressible flow is equal to 0,7.