Thermophysics and Aeromechanics

Ivanov, A. V.;Kachanov, Y. S.;Mischenko, D. A.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040014

Abstract The mechanism of production of nonstationary Görtler vortices in a boundary layer on concave wall by surface nonuniformities (vibrations and roughness) has been experimentally examined. The nonuniformities were produced by a specially developed disturbance source. They were controlled, localized along the streamwise coordinate, and periodic over the span of the experimental model. Tests in a low-turbulence wind tunnel have proved that the disturbance source is an efficient means of experimental study of the receptivity and stability problem for boundary layers dominated by Görtler instability. The operation of the disturbance source leads to the production of small-amplitude nonstationary Görtler vortices (tenth or hundredth fractions of a per cent of the free-stream velocity) with predefined characteristics (frequency and spanwise wavelength). In our experiments, we quantitatively examined the problem of linear receptivity of boundary layer to surface nonuniformities in a broad range of frequencies for the most dangerous spanwise scales of Görtler vortices. The values of the amplitudes and phases of the receptivity coefficients were determined. The amplitudes proved to be much smaller in magnitude in comparison with the excitation of modes of hydrodynamic instabilities of other types (Tollmien-Schlichting waves and cross-flow-instability modes). It was found that, with increasing the frequency, the amplitudes of the receptivity coefficients showed a distinct growth while for high frequencies those amplitudes also exhibited a growth with the spanwise scale of perturbations, although for stationary surface roughness no effect due to this scale was observed. It was found that the dependences on frequency of the efficiency of the mechanisms of stability and receptivity showed opposing behaviors, were in competition, and could partially compensate each other, promoting, thus, the production of boundary-layer Görtler vortices in a broad range of frequencies.

Goldfeld, M. A.;Zakharova, Yu. V.;Fedorova, N. N.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040026

Abstract Results of an experimental and numerical study of supersonic turbulent high-enthalpy flow in a channel with cavity are reported. On the basis of wind-tunnel tests performed in the IT-302M short duration wind tunnel, data on the flow structure and on the distribution of static pressure along the model walls were obtained. These data were subsequently used to verify the numerical algorithm. In the calculations, a parametric study of the effects of Mach number, cavity configuration, and temperature factor on flow quantities was performed. It was numerically shown that variation of the above parameters leads to a transition of the flow regimes in the vicinity of the cavity.

Gaponov, S. A.;Ermolaev, Yu. G.;Kosinov, A. D.;Lysenko, V. I.;Semenov, N. V.;Smorodskii, B. V.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040038

Abstract In the present study, we examined, both experimentally and theoretically, the influence of porouscoating thickness on the stability and laminar-turbulent transition of flat-plate supersonic boundary layer at free-stream Mach number M∞ = 2. A qualitative agreement between the data calculated by the linear theory of stability and the experimental data on the transition obtained for models with different porous-coating thicknesses was established. We show that with decreasing (within a certain interval) the porouscoating thickness the boundary layer becomes more stable to perturbations, and the laminar-turbulent transition, more delayed.

Lu, H. B.;Liu, W. Q.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S086986431204004X

Abstract This paper focuses on the design of a forward-facing cavity and opposing jet combined configuration for thermal protection system (TPS) of hypersonic vehicles. The cooling efficiency of the combined TPS was investigated numerically, and the numerical method was validated by the related experiment in the open literature. The flow field parameters, aerodynamic force, and surface heat flux distribution were obtained. The detailed numerical results show that this kind of combined TPS has an excellent impact on cooling the nose-tip, and it is suitable for the thermal protection of hypersonic vehicles which require long-range and time to cruise.

Perepelitsa, B. V.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040051

Abstract Results of experimental investigation of nonstationary temperature field in the flow and on the surface of the channel with corrugated wall are presented at a jump-like change of heat release in time. The changes were performed at the air flow in a rectangular channel, whose one heated wall was made as a plate with triangular corrugation oriented at 45° relative to the main flow direction. The microthermocouples with the thickness of below 10 microns were used to perform these changes. Investigations revealed typical regularities of temperature evolution in the flow and along the perimeter of the heated rib. Experimental data on time-temperature dependence are approximated well by the exponential function.

Bukreev, V. I.;Gusev, A. V.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040063

Abstract The article provides results of experimental investigation of a fresh water motion in a flume with limited dimensions at lateral heating. The initial water temperature in the flume ranged from 0 to 22 °C. It is shown that there are qualitative changes of the motion picture in the vicinity of initial temperature in the flume equal to the one at which water has maximal density (approximately 4 °C). At an initial temperature in the flume exceeding or equal to 4 °C, the heated water propagates in the form of a relatively thin surface jet, and at jet reflection from the flume end walls the heated water is accumulated only in the upper layer. When the initial temperature in the flume is below 4 °C the convective instability develops. A part of the heated water sinks to the bottom. The paper provides respective illustrations and quantitative data on the distribution of temperature and velocity.

Nigmatulin, R. I.;Filippov, A. I.;Khismatullin, A. S.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040075

Abstract The article describes the model of transcillatory heat transfer induced by gas bubbles buoyant in liquid. The temperature problem is reduced to the equivalent integral equation, and the velocity field in liquid phase is presented as structures of running and stationary waves. The relations for computing the coefficient of transcillatory transfer have been found.

Maltsev, L. I.;Zavarzin, D. S.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040087

Abstract Mathematical simulation of isothermal film flow for a viscous ponderous capillary liquid with dry spots on a solid substrate was performed. The algorithm was developed for calculation of the shape of a ridge (around the dry spot): this algorithm takes into account gravity forces, surface tension, friction, and inertia effects. Simulation results performed by original method were compared with experiment and previous method that takes into account only gravity and capillary forces. It was demonstrated that both methods produce similar results at low Reynolds numbers. However, at Reynolds higher than one these two methods give different results.

Thandapani, E.;Ragavan, A. R.;Palani, G.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040099

Abstract Free convection flow over an isothermal vertical cone immersed in a fluid with variable viscosity and MHD is studied in this paper. Using appropriate variables, the basic equations are transformed into the non-dimensional boundary-layer equations. These equations are then solved numerically using a very efficient implicit finite-difference method known as Crankl-Nicolson scheme. Detailed results for the velocity, temperature, skin friction, and heat transfer rates for a selection of parameter sets consisting of the viscosity parameter, magnetic field parameter, and Prandtl number are discussed. In order to validate our numerical results, the present results are compared with the available work in the literature and are found to be in an excellent agreement.

Rubtsov, N. A.

2012 Thermophysics and Aeromechanics

doi: 10.1134/S0869864312040105

Abstract Model interpretation of heating and melting processes is analyzed in application to the onephase statement of Stefan problem in a flat layer of semitransparent material heated from one side, and melted by the radiation-convective method.