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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.

Numerical investigation (A.I.Leontiev, V.G.Lushchik, A.E.Jakubenko «PARADOXES OF HEAT TRANSFER ON A PERMEABLE WALL») shows that adiabatic wall temperature in the region of the gas film may be lower than the injected gas (coolant) temperature. It occurs in case of foreign light-gas injection and it does not occur in case of uniform gas injection under the same conditions. This paper is devoted to the experimental investigation of this conclusion. Experimental researches have been conducted in the low flow-rate supersonic wind tunnel (Mach number of 3) located in the Institute of Mechanics of the Moscow State University. Argon was used as a primary stream, helium and argon as coolant. The coolant was blown in through the porous permeable part of a model and injected into the supersonic boundary layer. The surface temperature of the model was gained with use of the infrared scanning device ThermaCAM SC 3000. As a result following data have been obtained. It is shown in particular that the adiabatic wall temperature in the region of the gas film may be lower than the injected gas (coolant) temperature. This effect does not take place in case of uniform (air-air, argon-argon etc.) gas injection, for this effect is especially essential for gas mixtures with low values of the Prandtl number.