Gasdynamic design of a two-dimensional supersonic inlet with the increased flow rate factorGounko, Yu. P.;Mazhul, I. I.
2012 Thermophysics and Aeromechanics
doi: 10.1134/S086986431203002X
Abstract A two-dimensional inlet of external compression with the increased flow rate factor at high supersonic velocities is constructed by the method of gasdynamic design. Its feature is that a flow with the initial oblique shock wave and the subsequent centered isentropic compression wave is formed over the external compression ramp of the inlet. These waves interact with one another so that a resulting stronger oblique shock wave and a velocity discontinuity arise in front of the entrance to the inlet internal duct. An example of an inlet configuration with the design flow regime corresponding to the Mach number Md = 7 is considered. The characteristics of this inlet were obtained in the range of the free-stream Mach numbers M = 4–7 with the use of a Navier—Stokes code for turbulent flow. They are compared with characteristics of an equivalent conventional shocked inlet. As computations have shown, the inlet with the isentropic compression wave has much higher values of flow rate factor φ at Mach numbers M < Md. So, for example, at M = 4 the value φ ≈ 0.72 for it is by 33 % higher in comparison with φ ≈ 0.54 for the equivalent shocked inlet.
Numerical quadrature for the Prandtl—Meyer function at high temperature with application for airZebbiche, T.;Boun-jad, M.
2012 Thermophysics and Aeromechanics
doi: 10.1134/S0869864312030031
Abstract When the stagnation temperature of the combustion chamber or ambient air increases, the specific heats and their ratio do not remain constant any more, and start to vary with this temperature. The gas remains perfect, except, it will be calorically imperfect and thermally perfect. A new generalized form of the Prandtl-Meyer function is developed, by adding the effect of variation of this temperature, lower than the threshold of dissociation. The new relation is presented in the form of integral of a complex analytical function having an infinite derivative at the critical temperature. A robust numerical integration quadrature is presented in this context. The classical form of the Prandtl—Meyer function of a perfect gas becomes a particular case of the developed form. The comparison is made with the perfect gas model for aim to present a limit of its application. The application is for air.
Mixing in a T-shaped micromixer at moderate Reynolds numbersMinakov, A. V.;Rudyak, V. Ya.;Gavrilov, A. A.;Dekterev, A. A.
2012 Thermophysics and Aeromechanics
doi: 10.1134/S0869864312030043
Abstract In the present work, the regimes of the flow and mixing of fluids in a T-shaped micromixer in the range of the Reynolds numbers from 1 to 1000 are investigated systematically with the aid of numerical modeling. The flow and mixing regimes are shown to alter substantially with increasing Reynolds numbers. Five different flow regimes have been identified in the total. The dependencies of the friction coefficient and mixing efficiency on the Reynolds number are obtained. A sharp increase in the mixing efficiency at a flow transition from the symmetric to asymmetric steady regime is shown. On the other hand, the mixing efficiency slightly drops in the laminar-turbulent transition region. A substantial influence of the slip presence on walls on flow structure in the channel and mixing efficiency has been revealed.
Impact of acoustic oscillations on thermal tornado stabilityBelousova, A. O.;Golovanov, A. N.;Matveev, I. V.
2012 Thermophysics and Aeromechanics
doi: 10.1134/S0869864312030055
Abstract This paper presents physical modeling of thermal tornado under lab conditions. For the tested range of 0÷300 Hz, selective frequencies were discovered which facilitate the tornado decay. Data analysis was complemented by velocity profile measurement using LDV system LD-05M. The results on velocity pulsation at selected points were recalculated into coefficient of correlation between velocities and function cos(2πfΔt i ) describing the acoustic oscillations. In the theoretical part of this paper, we present solution of dispersive equation of Euler’s model and resulting boundary of stability for tornado existence. Satisfactory agreement between experiment and calculation has been observed.
Emission of Ag 2 dimers from a substrate during vacuum deposition of the mixture of silver and water vaporBochkarev, A. A.;Polyakova, V. I.
2012 Thermophysics and Aeromechanics
doi: 10.1134/S0869864312030092
Abstract The work presents calculation of Ag2 dimers emission from the substrate into the vapor medium in case of joint deposition of silver and water vapors on ideal substrate formally modeling the crystal of water ice in terms of energy properties. It is assumed that the dimers are formed on the condensation surface as a result of random collisions of atoms at their surface migration, and the dimers emission is conditioned by thermal fluctuations of crystal lattice of water ice. The calculations based on the modified Langmuir adsorption model allowed concluding that emission of silver and water dimers takes place in the entire range of the studied water vapor pressure, binding energy of silver-water, and crystal temperature. Dynamics of emission from the beginning of deposition and dependence of dimers emission on micro-roughness of the condensate surface have been investigated. Statistical processing of results has shown that the probability of dimers emission from the condensate surface is determined not only by the value of the binding energy between the dimer and condensate but by configuration of the nearest dimer environment on the condensation surface. It has been found that there is a certain value of micro-roughness of condensation surface providing the maximal intensity of dimer emission. Dimers emission from the surfaces bordering on the flows of vapor mixtures contaminates the flows with unsuspected admixtures. The latter one makes investigation of this phenomenon important for aeromechanics of vapor and gas mixtures.