Law of friction in the region of a gas screen behind a permeable section

The results are given of measurements of friction behind a permeable section in a subsonic turbulent boundary layer at blowing intensity j = 0.003–0.04. Methods are proposed for calculating the local coefficients of friction in the region of a gas screen and the Reynolds number determined from the momentum loss thickness; these are in satisfactory agreement with experiment.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 159–162, March–April, 1979.     

Experimental investigation of the effects of blowing conditions and Mach number on the unsteady behavior of coolant ejection through a trailing edge cutback

The present paper shows the results of an experimental investigation into the unsteadiness of coolant ejection at the trailing edge of a highly loaded nozzle vane cascade. The trailing edge cooling scheme features a pressure side cutback with film cooling slots, stiffened by evenly spaced ribs in an inline configuration. Cooling air is also ejected through two rows of cylindrical holes placed upstream of the cutback. Tests were performed with a low inlet turbulence intensity level (Tu₁ = 1.6%), changing the cascade operating conditions from low speed (M_2is = 0.2) up to high subsonic regime (M_2is = 0.6), and with coolant to main stream mass flow ratio varied within the 0.5–2.0% range. Particle Image Velocimetry (PIV) and flow visualizations were used to investigate the unsteady mixing process taking place between coolant and main flow downstream of the cutback, up to the trailing edge. For all the tested conditions, the results show the presence of large coherent structures, which presence is still evident up to the trailing edge. Their shape and direction of rotation change with injection conditions, as a function of coolant to mainstream velocity ratio, strongly influencing the thermal protection capability of the injected coolant flow. The Mach number increase is only responsible for a positioning of such vortical structures closer to the wall, while the Strouhal number almost remains unchanged.     

Displacement in the turbulent boundary layer on a permeable plate with supercritical injection

The displacement thickness in a turbulent boundary layer is determined for supercritical injection parameters. Experimental relations between the displacement thickness and the injection parameter are obtained for air, helium, and freon-12 injected into air.     

Two-temperature model of a plasma under conditions of stationary blowing of a gas through a plasmotron

Results are given of a calculation conducted on the basis of a two-temperature plasma model for a cylindrical arc in a channel with the blowing through of a gas. It is shown that the gas venting leads to the appearance of a considerable separation between the electron and gas temperatures near the wall of the plasmotron and in the cathode zones. The possibilities of the two-temperature model are analyzed from the point of view of an approximate calculation of the electron temperature in arc and induction plasmotrons. It is shown that the electron temperature can be estimated from simple relationships with at least 10% accuracy for induction and 15–20% accuracy for arc plasmotrons.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 3–12, July–August, 1973.     

Experimental investigation of the efficiency of gas screens at a burning-out surface with the blowing of a foreign gas

The article gives the results of a systematic experimental investigation of the efficiency of a gas screen at a burning-out graphite surface organized in different manners and with the blowing of a foreign gas into the boundary layer. In the experiments, the Reynolds number was varied within the limits R_Δ ≈ 1.2·10⁵ = 1.6·10⁶, R* ≈ 100–2000, R_Z = 2.3·10²–1.5·10⁴; the enthalpy factor of the nonisothermicity in the initial cross section varied from i_s/i₀ = 1 with the tangential blowing of nitrogen to i_s/i₀ ≈ 34 with the blowing of helium through the heated porous section.     

A unified treatment of mixed convection on a permeable horizontal plate

A problem of mixed convection on a horizontal plate is reconsidered assuming that the plate is subjected to a variable temperature or variable heat flux. The plate is considered permeable allowing blowing or suction of the fluid. The results of free and forced convection are obtained as special cases of this study of mixed convection. It is also shown that the results corresponding to prescribed temperature are related to those of prescribed surface heat flux by simple conversion formulae.

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Eine einheitliche Behandlung der Mischkonvektion bei einer durchlässigen horizontalen Platte

Zusammenfassung Ein Problem der Mischkonvektion bei einer horizontalen Platte ist in der Annahme erörtert worden, daß die Platte einer veränderlichen Temperatur und einem veränderlichen Wärmestrom ausgesetzt wird. Hierbei wurde die Platte als durchlässig für Einblasen und Absaugen des Fluids angenommen. Die Ergebnisse der freien und erzwungenen Konvektion wurden als Spezialfälle dieser Studie für Mischkonvektion erhalten. Es wird angezeigt, daß die Ergebnisse, welche die Temperatur beschreiben, mit denen die die Wandwärmestromdichte beschreiben, durch einfache Umrechnungsformeln in Verbindung gebracht werden können.

     

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.     

Effect of a pre-attached dynamic section on heat transfer in a turbulent boundary layer,with blowing

This paper gives the results of an investigation of the effect of an initial dynamic section on heat transfer with blowing. The experimental data obtained show that the preattachment of a section can have a considerable effect on the heat transfer. A method is proposed based on the use of the relative laws of heat transfer; in this case, the effect of the initial section is taken into account in terms of the Stanton number at an impermeable surface. The calculation is in satisfactory agreement with the experimental data obtained, as well as with the experimental data of other authors.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 126–131, November–December, 1971.     

Strong blowing on the surfaces of a body immersed in a supersonic gas stream

This article considers the problem of strong blowing on the surface of a body immersed in a supersonic gas flow. It is not difficult to show that for intense blowing the motion of the blown gas can be described by the Euler equations, and viscosity and transport effects appear only in the neighborhood of the contact surface separating the oncoming flow and the blown gas. It is shown that to a first approximation the pressure is constant across the layer and equal to the pressure at the contact surface.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, pp. 97–104, No. 5, September–October, 1973.     

Law of heat transfer in the region of a gas curtain

The article gives the result of an experimental investigation of heat transfer in the region of a gas curtain behind the permeable part of the surface in a subsonic turbulent boundary layer in the range of blowing intensities j=0.001–0.04.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 160–163, March–April, 1976.The authors thank G. A. Lyubimov for his continuing interest and aid in the work.     

Bending behavior of a rectangular plate with a bitrapezoidal cross section

A theory is developed for the transverse deflections when a rectangular plate having a bitrapezoidal cross section is subjected to a uniform longitudinal curvature. The theoretical solutions are compared with earlier results presented by Lamb and Fung and Wittrick. Experimental results are compared with the theory and good agreement is obtained over the range of curvatures tested.     

Distinctive features of heat transfer in the region of a gas curtain formed on injection of extraneous gas

New effects on a permeable surface on gas injection are detected on the basis of the numerical modeling of a turbulent boundary layer. It is shown, in particular, that in the gas curtain region the surface temperature can be considerably lower than the injected gas temperature. This effect manifests itself particularly strongly for gas mixtures with low Prandtl numbers.     

Effect of blowing on supersonic dust-laden gas flow round a blunt body

One of the main problems which arise in the design of high-speed aircraft is the protection of the streamline surfaces against the erosion effect of solid particles and drops occurring in the free stream. For this purpose it is possible to use the device of blowing cold gas. This leads to the formation of a boundary layer of high density in which the particles are decelerated [1]. The present study investigates the effectiveness of this method of erosion protection in the example of supersonic flow round a sphere.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 178–181, March–April, 1986.