M. M. Strongin

Effect of vortex flows at surface with hollow-type relief on heat transfer coefficients and equilibrium temperature in supersonic flow

Abstract This paper deals with the results of experimental investigation of supersonic flow stream lining of the surface, which has relief looking as series of spherical hollows. Using thermography method the temperature fields on the surface are obtained at Mach numbers of the flow between 2 and 3. The study of these fields at unsteady conditions allows obtaining distributions of local coefficients of heat transfer. The coefficients of equilibrium temperature in different surface regions are determined by temperature fields. It is shown that the availability of spherical hollows relief on the surface not only intensifies heat transfer but also leads to decrease of recovery equilibrium temperature coefficients. The structure of the flow at flow along of the surface with series of hollows relief is studied by visualization. The nature of shadgraph indicates vortexes outgoing from hollows to flow core.

Experimental investigation of the temperature stratification of an air flow through a supersonic channel with a central body in the form of a porous permeable tube

The results of an experimental investigation of the gasdynamic temperature separation (stratification) of a supersonic air flow are presented. It is shown that in an axisymmetric supersonic channel the presence of a central body in the form of a cylindrical tube consisting of impermeable and permeable sections leads to the redistribution of the total energy of the flow. At the central body exit the mass-mean stagnation temperature of the air increases compared with its initial temperature.

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

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.Copyright

Film Cooling Efficiency in the Supersonic Flow With Foreign Gas Injection

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.Copyright