Thermophysics and Aeromechanics

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020019

Boiko, A. V.;Dovgal, A. V.;Kozlov, V. V.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020020

Abstract As a result of long-standing studies of subsonic flows past 2D surface imperfections, physical models to describe the influence of such elements on the boundary-layer transition to turbulence were formulated. The models are primarily based on stability properties of the flow around local geometrical variations of the wall. The present review discusses the mechanisms of boundary layer destabilization by the imperfections revealed by the classical analysis of low-amplitude shear layer oscillations and using recently developed approaches to the local/global modal/non-modal flow stability. While preparing this review, we preferred to trace and briefly outline the main routes of flow turbulization instead of discussing relevant details reported in original publications.

Kornilov, V. I.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020032

Abstract The possibility of using the injection of air into the incompressible turbulent boundary layer of an axisymmetric wing through a finely perforated area provided on the wing surface was studied. The air blowing was implemented via the supply of external pressurized flow through a permeable leading edge of the wing. It is shown that, with the blowing section located on the “flat” side of the wing, only an insignificant reduction in airfoil drag could be achieved. Simultaneously, the data obtained show that there exists a possibility of raising the lift-drag ratio due to a more appropriate choice of blowing-section location in the rarefaction region of the flow.

Krause, M.;Gaisbauer, U.;Kraemer, E.;Kosinov, A. D.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020044

Abstract The recovery ratio of a wedge-shaped hot-film probe was determined in an experimental as well as numerical study, since this information is still unpublished and essential for using the probe in hot-film anemometry. The experiments were conducted at the Khristianovich Institute of Theoretical and Applied Mechanics (ITAM) in Novosibirsk, Russia, and the simulations were performed with StarCCM+, a commercial 2nd order finite volume code. In the analysis, the Mach number was varied between M = 2 and M = 4, and the unit Reynolds number ranged from Re1 = 3.8•106 to Re1 = 26.1•106 m−1, depending on the Mach number. During the experiment, the stagnation temperature was kept constant for each Mach number at a separate value in the range of T 0 = 289 ± 7 K. Three different stagnation temperatures were used in the simulations: T 0 = 259 K, T 0 = 289 K, and T 0 = 319 K. The difference between the experimental and the numerical results is ≤ 0.5 %, and, therefore, both are in very good accordance. The influence of the Mach number, of the unit Reynolds number, and of the stagnation temperature was analysed, and three different fitting functions for the recovery ratio were established. In general, the recovery ratio shows small variations with all three tested parameters. These dependencies are of the same order of magnitude.

Kaplun, A. B.;Meshalkin, A. B.;Dutova, O. S.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020056

Abstract Using the previously obtained dependence of excess viscosity on internal energy density and low-parametric unified equation of state for calculation of thermodynamic properties of liquid, gas, and fluid, the equation for the excess viscosity of argon in the range of the “mixed” mechanism of momentum transfer in the shear flow was derived. Different versions of approximation of excess viscosity dependence on the density of interaction energy were compared, and the optimal version of this dependence was determined. A simple unified low-parametric equation was obtained for describing the coefficient of argon viscosity in a wide range of state parameters. It is shown that the proposed low-parametric equation for calculating the viscosity coefficient of liquid and gas allows reliable extrapolation beyond the studied region.

Klinkov, S. V.;Kosarev, V. F.;Ryashin, N. S.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020068

Abstract This paper presents experimental and simulation results of cold spray coating deposition using the mask placed above the plane substrate at different distances. Velocities of aluminum (mean size ~ 30 μm) and copper (mean size ~ 60 μm) particles in the vicinity of the mask are determined. It was found that particle velocities have angular distribution in flow with a representative standard deviation of 1.5–2 degrees. Modeling of coating formation behind the mask with account for this distribution was developed. The results of model agree with experimental data confirming the importance of particle angular distribution for coating deposition process in the masked area.

Arefyev, K. Yu.;Voronetsky, A. V.;Suchkov, S. A.;Ilchenko, M. A.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S086986431702007X

Abstract The work is devoted to the determination of main peculiarities of the two-phase mixture formation in the flow duct of the gas-dynamic ignition system. The paper presents a mathematical model and the results of a numerical and experimental investigation of the peculiarities of the unsteady gas flow as well as the processes of the fragmentation and evaporation of droplets in the resonance cavity of the gas-dynamic ignition system. Different configurations of injectors for liquid supply are considered, and the influence of the most significant factors on heat release and concentration of the evaporated liquid in the resonance cavity is investigated. The obtained data may be used for choosing the injectors and the regimes of the liquid fuel supply, which enable one to ensure the stable conditions for igniting two-phase fuel mixtures in the gas-dynamic ignition system.

Derevich, I. V.;Galdina, D. D.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020081

Abstract The Pontryagin equation was applied to calculating the average time for the random process escaping the assign interval: this gives the average delay time for waiting of particle ignition moment in a turbulent flow of gas. A direct numerical simulation method was developed for gas temperature fluctuations with assigned autocorrelation function and particle temperature fluctuations due to exothermal chemical reaction. The method was based on numerical solution of a system of stochastic differential equations. Results of direct simulation were validated through comparing with the analytical solution available for particles without exothermal reaction. Analytical calculations and results of direct numerical simulation for the delay time of particle ignition are in agreement.

Laptev, A. G.;Lapteva, E. A.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317020093

Abstract An approach to the determination of the heat and mass transfer coefficients from dispersed particles by the development of the hydrodynamic analogy is considered. The equations for computing the heat and mass transfer coefficients in continuous phase at a laminar regime of the flow around solid particles as well as the mass transfer coefficients in droplets are obtained. Comparisons with the experimental data of different authors are presented.

Vetrov, V. V.;Vorobyev, A. A.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S086986431702010X

Abstract The phenomenon of the intensification of convective heat transfer through air cavities under the conditions of their axial rotation and external heating based on the rise of centrifugal body forces in differently heated air medium has been substantiated theoretically and confirmed experimentally. The criterion dependencies for convection coefficients of axisymmetric cylindrical and conical closed air cavities subjected to external heating and axial rotation have been obtained using the results of the physical and numerical experiments. Both single-layer cylindrical cavities and two-layer ones with perforating internal orifices have been considered.