Thermophysics and Aeromechanics

Zvegintsev, V. I.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060014

Abstract Modern concepts of operation of supersonic inlets of high-velocity air-breathing engines are analyzed. It is demonstrated that the flow in the engine duct becomes extremely complicated in off-design modes of inlet operation, which can lead to unpredictable consequences, in particular, to inlet unstart. The term “inlet unstart” is considered in the present paper as a synonym of the absence of theoretical understanding and prediction of gas-dynamic phenomena. Various approaches are proposed to ensure self-regulation of the inlet-combustor system for air-breathing engines. Possible directions of further research are indicated for the purpose of stable operation of inlets in a wide range of flight conditions.

Yang, Z.;Tang, Z.-Y.;Cai, G.-B.;He, B.-J.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060026

Abstract A coupled NS-DSMC method possessing adapted-interface and two-way coupling features is studied to simulate the plume impingement effects of space thrusters. The continuum-rarefied interface is determined by combining KnGL and Ptne continuum breakdown parameters. State-based coupling scheme is adopted to transfer information between continuum and particle solvers, and an overlapping grid technique is investigated to combine structured-grid NS code and Cartesian-grid DSMC code to form the coupled solver. Flow problem of a conical thruster plume impinging on a cone surface is simulated using the coupled solver, and the simulation result is compared with experimental data, which proves the validity of the proposed method. Plume flow while the ascent stage of lunar module lifting off in lunar environment is also computed by using the present coupled NS-DSMC method to demonstrate its capability. The whole flow field from combustion chamber to the vacuum environment is obtained, and the result reveals that special attention should be paid to the plume aerodynamic force at the early stage of launching process.

Anufriev, I. S.;Sharypov, O. V.;Dekterev, A. A.;Shadrin, E. Yu.;Papulov, A. P.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060038

Abstract The flow pattern was studied for a four-vortex furnace of a coal-dust boiler. The paper presents results of experimental study of inner aerodynamics performed on a lab-scale isothermal model of the furnace device. The PIV method was used to receive the flow velocity fields for several cross sections. The analysis was performed for the spatial structure of the flow comprising four stable closed vortices with vertical axes of flow swirling.

Bui, V. T.;Kalugin, V. T.;Lapygin, V. I.;Khlupnov, A. I.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S086986431706004X

Abstract With the use of ANSYS Fluent software and ANSYS ICEM CFD calculation grid generator, the flows past a wing airfoil, an infinite cylinder, and 3D blunted bodies located in the open and closed test sections of low-speed wind tunnels were calculated. The mathematical model of the flows included the Reynolds equations and the SST model of turbulence. It was found that the ratios between the aerodynamic coefficients in the test section and in the free (unbounded) stream could be fairly well approximated with a piecewise-linear function of the blockage factor, whose value weakly depended on the angle of attack. The calculated data and data gained in the analysis of previously reported experimental studies proved to be in a good agreement. The impact of the extension of the closed test section on the airfoil lift force is analyzed.

Demenkov, A. G.;Chernykh, G. G.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060051

Abstract Numerical simulation of the decay of a momentumless swirling turbulent wake of a body of revolution has been carried out. It has been shown that beginning with the distances of the order of 1000 body diameters, the flow passes to the self-similar regime. Using the results of the numerical analysis of the flow, simplified mathematical models of far wake have been constructed.

Okhotnikov, D. I.;Molochnikov, V. M.;Mazo, A. B.;Malyukov, A. V.;Goltsman, A. E.;Saushin, I. I.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060063

Abstract Here we present the results of experimental investigation of a cross flow around a circular cylinder mounted near the wall of a channel with rectangular cross section. The experiments were carried out in the range of Reynolds numbers corresponding to the transition to turbulence in a wake of the cylinder. Flow visualization and SIV-measurements of instantaneous velocity fields were carried out. Evolution of the flow pattern behind the cylinder and formation of the regular vortex structures were analyzed. It is shown that in the case of flow around the cylinder, there is no spiral motion of fluid from the side walls of the channel towards its symmetry plane, typical of the flow around a spanwise rib located on the channel wall. The laminar-turbulent transition in the wake of the cylinder is caused by the shear layer instability.

Kulikov, Y. M.;Son, E. E.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060075

Abstract The paper presents key results on a large-scale entrainment of thermoviscous liquid layers with different temperatures and their further mixing observed in the plane-parallel flow with an inflectional velocity profile. We show that the instability development in the channel is more intensive at the inflection point vicinity and is not related directly to vorticity generation in the near-wall region. The considered flow being unstable relative to the finite-amplitude harmonic disturbances possesses several resonant frequencies initiating the most intense entrainment. Temperature fields are analyzed based on the time-averaged entrainment layer thickness and temperature isoline displacement. We discuss the spectral properties of flow enstrophy, vorticity, and kinetic energy in terms of asymptotics of cascades observed and coherent structures. Okubo-Weiss criterion is used for mapping of four flow zones wherein an active filamentation of the turbulent veil or long-term existence of vortex structures is possible.

Kudinov, V. A.;Eremin, A. V.;Kudinov, I. V.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060087

Abstract The differential equation of heat transfer with allowance for energy dissipation and spatial and temporal nonlocality has been derived by the relaxation of heat flux and temperature gradient in the Fourier law formula for the heat flux at the use of the heat balance equation. An investigation of the numerical solution of the heat-transfer problem at a laminar fluid flow in a plane duct has shown the impossibility of an instantaneous acceptance of the boundary condition of the first kind — the process of its settling at small values of relaxation coefficients takes a finite time interval the duration of which is determined by the thermophysical and relaxation properties of the fluid. At large values of relaxation coefficients, the use of the boundary condition of the first kind is possible only at Fo → ∞. The friction heat consideration leads to the alteration of temperature profiles, which is due to the rise of the intervals of elevated temperatures in the zone of the maximal velocity gradients. With increasing relaxation coefficients, the smoothing of temperature profiles occurs, and at their certain high values, the fluid cooling occurs at a gradientless temperature variation along the transverse spatial variable and, consequently, the temperature proves to be dependent only on time and on longitudinal coordinate.

Saedodin, S.;Barforoush, M. S. M.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060099

Abstract In this paper, the hyperbolic heat conduction equation in a cylinder subjected to a special heat flux boundary condition is solved. Equations are solved by deriving the analytical solution using separation of variables method. The temperature layers and profiles of sample calculations are presented. The wavy nature of this kind of heat conduction can easily be seen in the temperature profiles. It is found that with the increasing Vernotte number, a point can get to higher temperature during the process. Also, it can be perceived from temperature profiles that it is possible that the temperature of different points of object becomes even lower than the initial temperature.

Teslenko, V. S.;Drozhzhin, A. P.;Medvedev, R. N.

2017 Thermophysics and Aeromechanics

doi: 10.1134/S0869864317060105

Abstract The paper describes experimental modeling of combustion of a stoichiometric propane-oxygen mixture in quasi-cylindrical bubbles with non-smooth interface using polyvinyl chloride tubes with barriers inside (multiple or single water droplets; or the balls of polystyrene and steel). The transition from combustion to detonation occurs both before and after the barrier, for any kind of barrier material.