Thermophysics and Aeromechanics

Levin, V. A.;Afonina, N. E.;Gromov, V. G.;Smekhov, G. D.;Khmelevsky, A. N.;Markov, V. V.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030013

Abstract Full-scale and computational experiments were used to investigate the flows in the jet thrust unit with annular nozzle and deflector in the form of a spherical segment. The used working gas was the combustion products of air mixtures with acetylene, gas-phase aviation kerosene, and natural gas. Experimental studies were carried out in a hot-shot wind tunnel in the range of stagnation pressure from 0.48 to 2.05 MPa. The calculations for the cases of combustion products outflow in terrestrial and high altitude conditions were performed with the original computer program that used the Euler and Navier-Stokes systems supplemented by equations of chemical kinetics. It was found that the thrust of the jet module with an annular nozzle at high altitude almost twice exceeds the sound nozzle thrust, but is lesser (about 25 %) than the thrust of the ideal calculated Laval nozzle; the difference therewith decreases markedly with the decrease of flight altitude and stagnation pressure.

Sobolev, A. V.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030025

Abstract An experimental investigation of the influence of mixing intensification by small-size jets on the startup and characteristics of a gas ejector with central nozzle and a convergent mixing chamber is carried out. It is shown that at high flow rates of the secondary gas, the critical regime is not settled because of the formation of a thick subsonic layer near the chamber wall. In these cases, a stepwise startup was done. The range of critical regimes is limited by the reloading point, at which the velocity near the chamber wall becomes sonic. The critical regime breakdown behind the reloading point occurs due to the upstream propagation of the back pressure through the subsonic layer. The mixing intensification ensures the equalization of the velocity profile and the extension of the range of critical regimes. Despite the improvement of characteristics the mixing in an ejector with the central nozzle remains incomplete. Experimental characteristics are compared with the computed ones. The mixing process is isobaric in the computation without the consideration of dissipative losses because of which the rise of the pressure of a mixture of primary and secondary gases occurs.

Zubkov, P. T.;Yakovenko, A. V.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030037

Abstract The influence of vibration on the behavior of the perfect viscous gas inside a rectangular cavity is investigated numerically. The heat and mass transfer processes in gas are compared in the region under the isothermal and adiabatic boundary conditions. The problem is solved in the one-dimensional statement.

Kornilov, V. I.;Boiko, A. V.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030049

Abstract A possibility to simulate a thick Clauser-equilibrium incompressible turbulent boundary layer on a flat plate of finite length with the help of a grid formed by cylindrical rods was experimentally examined. A grid with rods oriented parallel to the streamlined surface proved to be an efficient tool enabling modification of the turbulent boundary layer. In most cases, at a distance of 600 rod diameters the time-average and fluctuation characteristics of the modified boundary layer exhibited values typical of a natural turbulent boundary layer. It is shown that the mean velocity profiles with artificially increased boundary-layer thickness can be represented, to a good accuracy, in terms of law-of-the-wall variables, and they can be generalized with a single dependence using an empirical velocity scale in the outside region. The use of a combined method for exerting an influence on the shear flow capable of improving the modeling procedure for turbulent velocity fluctuations in boundary layer is proposed.

Semenov, B. N.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030050

Abstract The conditions for possible reduction of hydrodynamic resistance by the compliant coatings are considered from two points of view: pulling the laminar flow and alteration of turbulence generation in the near-wall zone. A strong effect of the longitudinal pressure gradient and reasonability of the search for the laminarized bypass flows in the presence of compliant coatings are distinguished.

Zharkova, G. M.;Kovrizhina, V. N.;Petrov, A. P.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030062

Abstract Results of a study of the optical response of liquid crystals with helical supramolecular structure to surfacefriction-induced shear stress in aerodynamic experiments are reported. The effect of re-orientation of molecules from confocal (light-scattering) to planar (selectively reflecting light) texture is considered. The textural transition is examined by the spectral and colorimetric methods. Dependences of the reflection spectra of the formed planar texture on time and on the mean shear-stress level were obtained. It is shown that the dependence of the texture transition time on the shear-stress level can be approximated, in a logarithmic scale, with a linear dependence; this allows using the effect for flow diagnostics.

Aktershev, S. P.;Kuibin, P. A.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030074

Abstract A new method of solution to the problem of stability of the swirl flow of viscous incompressible fluid is developed. The method based on expansion of the required function into power series of radial coordinate allows an avoidance of difficulties related to numerical integration of the system of differential equations with a singular point. Stability of the Poiseuille flow in a rotating pipe is considered as an example.

Kuraev, A. A.;Semenov, A. B.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030086

Abstract Results of a parametric study of pressure characteristics of a perforated membrane in an oscillating liquid flow are reported. A diagram of an experimental facility for evaluation of the pressure produced by a perforated membrane in an oscillating flow is given.

Tairov, E. A.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030098

Abstract A theoretical study of the equilibrium velocity of sound in the liquid-vapor mixture containing the close-packed layer of spherical particles has been carried out. Thermodynamic relations include a description of a non-stationary heat transfer between the mixture and particles in compression half-wave. The theoretical model allows explaining the experimentally observed significant reduction in the equilibrium velocity from its adiabatic value at the increase in vapor content of the mixture. The calculated results agree with experimental data obtained in the vertical channel at filtering the liquid-vapor mixture in a close-packed layer of spherical particles of borosilicate glass and steel.

Shagapov, V. Sh.;Khasanov, M. K.;Gimaltdinov, I. K.;Stolpovsky, M. V.

2013 Thermophysics and Aeromechanics

doi: 10.1134/S0869864313030104

Abstract Results of numerical simulation of warm gas injection into a porous medium initially saturated with gas and gas hydrate, accompanied by gas hydrate dissociation, are presented. It is shown that depending on parameters at the outer boundary of the medium (permeable or impermeable to the gas flow) hydrate dissociation can occur both at the frontal boundary and in the extended region.