Home – Home – Jornals – Thermophysics and Aeromechanics 2002 number 3

A database developed at the Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences is described, which is designed to store both experimental and numerical results in the field of aerodynamics. The system is constructed using the client-server technology. The software operates on various platforms (Linux, Windows). Experimental data are compared with numerical simulations performed using the system proposed.

The peculiar features of fluctuation diagrams are analysed at subsonic and supersonic velocities of the flow for acoustic disturbances propagating at some angle to the flow. It is shown that location of minimum of the fluctuation diagram for an acoustic mode depends on the direction of acoustic wave propagation; the diagram is either a line segment or consists of two sections in the form of letter V with its vertex on an abscissa axis. At subsonic flow velocities a cross point of the fluctuation diagram for the acoustic mode with the abscissa axis is always farther from a coordinate origin than the similar point for the vortical mode. At supersonic velocities an inverse picture is observed. The relations between the fluctuation diagram and the acoustic disturbance characteristics have been obtained. It is found that the V-formed fluctuation diagrams  at supersonic velocities correspond to the acoustic disturbance sources moving in the flow only at subsonic difference of the flow velocities and sources. In case when the coordinate of a cross point of the diagram continuation with the abscissa axis is negative, a linear diagram of fluctuations can correspond to both subsonic and supersonic differences of the flow velocities and sources.

The gas oscillations arising in a planar duct under the excitation of a wall part are studied numerically on the basis of the solution of an aeroelasticity problem. A spatial localization of transverse and streamwise waves has been revealed computationally, and the character of the power spectra of pressure oscillations upstream and downstream of the excitation region has been established.

Results of experimental studies of relaxation properties of an incompressible two-dimensional turbulent boundary layer under the conditions of an adverse pressure gradient influence and disturbed by a circular cylinder with D/δ₀

The receptivity of a flat-plate boundary layer with a positive (adverse) pressure gradient with respect to 3D localized surface vibrations is investigated. The experiment was carried out under controlled disturbance conditions using two wave-train sources in the form of circular vibrators. The wave trains (consisting of Tollmien ( Schlichting waves) had been decomposed into oblique normal (harmonic in time and space) modes. The curves of growth of amplitudes and phases of the normal modes, obtained using the main source, were extrapolated to the position of its center by means of the corresponding curves obtained from the additional source located upstream. The shape and the amplitude of the surface vibrations were accurately measured by a noncontact optical system. After deep processing of the experimental data, the complex coefficients of the boundary layer receptivity to 3D surface vibrations were determined for four values of the disturbance frequency as functions of the spanwise wavenumber and the wave inclination angle to a flow direction. The calculations were performed within the framework of a linear receptivity theory for the experimental conditions under assumptions of a local flow parallelism. A good agreement between the experimental and theoretical receptivity coefficients is found. The flow under investigation is shown to be significantly more receptive to three-dimensional surface vibrations in comparison with two-dimensional ones. The receptivity amplitude increases with frequency, especially for the modes inclined at large angles to the flow direction. The positive pressure gradient is found to lead to a reduction of the vibration receptivity, especially for 3D modes.

According to analysis of parameters specified for the problem of interference interaction between a compliant boundary and a viscous sublayer, there is a strong dependence of calculated phase-frequency area with positive action (PFAPA) of the boundary (i.

The modelling of ramjet operation based on the numerical solution of the Euler equations in the

The technology of adiabatization of a boundary layer of a vortex flow above the plane was studied for an arbitrary distribution of the azimuthal velocity by the radius. Experiments confirmed a drastic reduction in the heat flux density, so the vortex flow can be considered as a heat protection for heat transfer surfaces.

The heat transfer on the inner surface of a supersonic channel with a set of consecutive cavities was studied. Experiments demonstrated a strong influence of these cavities on the distribution of heat transfer, on appearance of zones with peak heat loads and on a higher level of heat transfer in lengthy zones between the cavities and downstream of them. In the framework of integral method of heat transfer calculation, we used the model function of the pressure gradient impact on the turbulent transfer. Calculations demonstrated a reproducible rate of relaxation processes behind the shocks and rarefaction waves. A rather strong effect of turbulent transfer was reconfirmed for the flow zones subjected to the rarefaction waves.

A dynamical thermal mathematical model in concentrated parameters, the numerical algorithm, and software are developed, and some results of computations of radiation and conductive heat transfer processes in a block-module design of a non-gas-tight equipment module of promising long-life spacecraft for communication and telecommunication are presented for conditions of operation in a geostationary orbit.

Analysis of systematic fuel saving demonstrates that steam-gas technology for modernization of a coal-dust power plant provides energy saving. The methods and formulas were developed for estimation of the systematic energy saving. It was demonstrated that the highest degree of fuel saving in the system is achieved at a high duality ratio and with heat load regime covered completely without use of a peak-load boiler.

A physico-mathematical model is proposed for the motion of liquefied gas and small ice particles within the framework of one-velocity one-temperature approximation of the mechanics of non-equilibrium heterogeneous media. On its basis the problem of transporting a mixture for long distances is considered. An estimate is given for the nonequilibrium effect of the process of ice melting on flow parameters. The distances between the pump and refrigerator stations are determined, which are needed for the cryogenic pipeline operation.

The problems of the non-wetting liquid (oil) displacement by a wetting liquid (water) are analysed numerically for the one-dimensional case in physical variables. It is shown that for increasing the recovery the use of a hot displacing agent is more preferable than the use of cold displacing agent. To increase the value of frontal saturation the alteration of the viscosity of phases is more efficient.

The thermal conductivity of gaseous 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) was studied over the temperature range from 300 to 423 K at pressures up to 2.4 MPa. The measurements were carried out with a steady-state coaxial-cylinder method. The purity of samples used throughout the measurements was 99.4 mol %. The uncertainties in the obtained thermal conductivity data are estimated to be less than

This paper studies one of the methods for production of a hydrophobic surface. This study is based on the method, which allows substitution of the polar hydroxyl group ((

The equations are formulated for the transfer of particles of bidisperse suspension in a disk centrifuge with regard for the interaction of particles with each other and with ambient liquid. The effect of initial concentration of particles on their sedimentation velocity and the sediment layer formation are studied. A possibility is shown for the formation of an internal wave of concentration of small particles as the result of the entrainment of small particles by large particles. The applicability of the formula for numerical differentiation is shown, which describes the temporal variation of particles concentration to determine sedimentation velocity.