Nonisothermal rarefied gas flow through a narrow slit

The nonisothermal flow of gas through a narrow slit under the influence of small pressure and temperature differences is investigated. The flow field and the mass and heat fluxes are found. It is shown that the heat transfer between the gas and the diaphragm, caused by the pressure difference, leads to a thermal polarization effect. The Onsager reciprocity relation is checked.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 171–175, July–August, 1990.     

Flow regimes with temperature extrema is the motion of a gas through a porous medium

Self-similar solutions are obtained for the problem of the motion of a heated gas through a porous medium with allowance for heat transfer between the gas and the solid phase in accordance with Newton's law. It is shown that there exist flow regimes in which the gas temperature increases with distance in the direction of motion.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 71–77, July–August, 1987.     

Heat transfer in a very rarefied gas

A one-dimensional problem of heat transfer in a rarefied gas is considered. It relates to the nonmonotonic variation of the heat flux between two plates when the temperature of one of them is reduced. Attention is drawn to a paradox that arises in this problem if the interaction of the molecules of the gas with the surface is described by means of accommodation coefficients.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1. pp. 195–198, January–February, 1980.     

Thermal effect of a freely expanding gas jet on a flat plate

An experimental investigation was made into the thermal effect of a single gas jet on a plate at Mach numbers of the nozzles in the range 2–6.1, specific heat ratio = 1.4, total pressure difference up to 6·10⁷, gas temperature 450–520 °K in the forechamber, and pressure in the forechamber (10–20)· 10⁵ Pa. The proposed dimensionless numbers made it possible to obtain generalized dependences of the distribution of the heat flux to the plate on the conditions of the problem. A method of approximate calculation of the heat fluxes is proposed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 119–126, July–August, 1981.     

Thermophoresis and photophoresis in a rarefied gas

The present article discusses the problem of the force acting on a spherical particle in a heated rarefied gas (thermophoresis) and the problem of the force acting on such a particle in an isothermal rarefied gas, heated by an external heat flux (photophoresis). Both problems are solved in a linear statement, i.e., under the assumption of the smallness of the temperature gradient of the gas and of the external heat flux, respectively. The rising interest in these problems is due to problems of atmospheric contamination, the physics of clouds, etc.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 178–182, September–October, 1976.     

Self-similar movement of a viscous gas in a channel

The results presented in [1] refer primarily to dropping liquids for which the influence exerted by the thermal conditions on the flow is related to the temperature dependence of the viscosity. The self-similar flow of a viscous gas in a channel with a linearly increasing wall temperature is examined in this paper. The influence exerted by the Reynolds and Prandtl numbers on heat exchange and the hydrodynamics of the flow is analyzed.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 47–54, May–June, 1976.The author wishes to thank A. F. Seleznev for carrying out the calculations and V. N. Shtern for discussing the paper.     

Supersonic gas flow over a wavy surface

Exact numerical solutions of the problem are obtained for a compressible viscous heat-conducting gas flowing over a slightly wavy surface. The effect of the free-stream parameters on the stresses, the temperature fields and the heat fluxes at the wavy interface is studied in detail.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 15–22, November–December, 1988.     

Ignition of a gas in a boundary layer at a heated plate

The problem of the ignition of a moving homogeneous gaseous combustible mixture in a boundary layer along a heated flat semiinfinite plate is one of the main problems of the ignition of a combustible mixture in a flow (for example, [1]). The formulation of the problem includes the two-dimensional equations of motion and the equations of the transfer of heat and of the reacting substance, written taking a chemical reaction into consideration, as well as boundary conditions, and should lead to determination of the steady-state fields of the concentration and the temperature and, by the same token, of the position of the combustion zone. Different approximate numerical solutions of the problem were analyzed in [1–5]. One of the most important characteristics of the process is the length of the ignition, i.e., the distance from the edge of the plate to the point at which, thanks to the intrinsic chemical heat evolution in the gas, the heat flux from the plate to the gas becomes equal to zero. In the present work, for the case of large values of the activation energy of the chemical reaction and a sufficiently great temperature difference between the wall and the flow, an approximate expression is obtained for the length of the ignition.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 142–148, September–October, 1977.The authors thank V. M. Shevtsov for his aid in making the calculations.     

Thermomechanical oscillations of a fluidized bed

Within the framework of the simplest one-dimensional model of a fluidized bed as a medium consisting of two interpenetrating interacting fluids, it is shown in the paper that linear thermomechanical oscillations can occur if the gas viscosity depends on the temperature and a nonisothermic chemical reaction takes place in the fluidized bed. The conditions under which oscillations occur and their frequencies are determined and their dependence on the fluidization parameters, the heat loss (or supply) rate, the rate and heat of the reaction, and quantities characterizing the dependence of the gas viscosity on the temperature and the force of the interphase interaction on the concentration of the solid particles is found.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 75–80, September–October, 1984.     

Convection of a viscous incompressible gas in rectangular regions with inlet and outlet channels

A study is made of two-dimensional problems of thermal convection of a viscous incompressible gas in rectangular regions that have gas inlet and outlet channels in the presence of a temperature difference between the bottom and the top (the bottom is heated). In contrast to the well-studied case of natural convection, when no-slip conditions are specified on all boundaries of the region and motion in the region occurs only through the temperature difference [1–4], the heat transfer in the investigated flows is complicated by the additional influence of the forced convection of the gas due to the motion of gas through the inlet and outlet channels. Flows of such type simulate well the processes that take place in many heat transfer devices and in ventilated and air-conditioned industrial premises. Two formulations of the problem are considered. In the first, the gas flow through the inlet and outlet channels is assumed given, and the solution of the problem is determined by the dimensionless Prandtl, Grashof, and Reynolds numbers. In the second case, this flow rate is not given but determined during the solution of the problem. The motion in the region arises from the difference between the temperatures of the bottom and the top of the region, and the motion, in its turn, causes a flow of gas through the inlet and outlet channels. As in the case of natural convection, the solution of the problem in this case is determined by only two dimensionless numbers — the Grashof and Prandtl numbers. By numerical solution of the boundary-value problems for the equations of heat transfer a study is made of the influence of the characteristic dimensionless numbers on the hydrodynamic and temperature fields and the heat fluxes through the boundaries of the region. The solutions of the problems in the two formulations are compared for different positions of the outlet channels.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 126–131, September–October, 1979.We thank G. I. Petrov for discussing the results.     

Calculation of a Heat Flow from a Spherical Particle in a Diatomic Gas

The problem of heat flow from a uniformly heated spherical particle in a diatomic gas is considered. The paper reports results of numerical calculations for an analog of the Bhatnagar–Gross–Krook model of the collision integral under for purely diffuse reflection of the gas molecules from the surface.     

Experimental study of heat and mass transfer from a horizontal cylinder in downward air-water mist flow with blockage effect

An experimental study was made on convective heat and mass transfer from a horizontal heated cylinder in a downward flow of air-water mist at a blockage ratio of 0.4. The measured local heat transfer coefficients agree fairly well with the authors' numerical solutions obtained previously for the front surface of a cylinder over the ranges mass flow ratio 0–4.5×10⁻², a temperature difference between the cylinder and air 10–43 K, gas Reynolds number (7.9–23)×10³, Rosin-Rammler size parameter 105–168 μm, and dispersion parameter 3.4–3.7. Heat transfer augmentation, two-pahse to single-phase of greater than 19 was attained at the forward stagnation point. For heat transfer in the rear part of the cylinder, an empirical formula is derived by taking into account the dimensionless governing variables, that is, coolant-feed and evaporation parameters.     

Investigation of the stability of a heavy fluid film in a hot heat-conducting gas jet on an inclined phase-transition surface

The stability of the flow of a heavy viscous fluid film flowing along the inclined phase-transition surface is examined. In contrast to [1] wherein it was assumed that a constant temperature is maintained on the free surface, it is assumed here that the fluid film is on the boundary with a gas jet which has finite specific heat and heat conduction. In this connection, the stability criteria differ substantially from [1].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 10–18, July–August, 1974.     

Heat transfer in a turbulent boundary layer with stepped injection

The asymptotic theory of a turbulent boundary layer has been applied to derive relationships for the heat and mass transfer when there is injection and consequent nonuniformity in the gas composition. Experimental studies are reported on heat and mass transfer with stepped injection of homogeneous and inhomogeneous gases; the results confirm the equations for the heat and mass transfer at a permeable surface when a foreign gas is blown in.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 124–129, July–August, 1973.     

Flow in the neighborhood of the stagnation line on a blunt body traveling at supersonic speed through a zone with elevated temperature and vibrational energy of the molecules

The unsteady flow in the neighborhood of the stagnation line on a sphere traveling at supersonic speed through a plane layer of diatomic gas with elevated temperature and nonequilibrium excitation of the molecular vibrations is investigated. (The source of the inhomogeneity could be a gas discharge [1].) The problem is solved using the viscous shock layer model which makes it possible to take molecular transport processes into account and analyze the unsteady heat transfer. Such flows were previously calculated in [2] within the framework of the inviscid gas model.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i GazNo. 3, pp. 183–185, May–June, 1990.     

Euler–Lagrange/DEM simulation of wood gasification in a bubbling fluidized bed reactor

We present an Euler–Lagrange method for the simulation of wood gasification in a bubbling fluidized bed. The gas phase is modeled as a continuum using the 2D Navier–Stokes equations and the solid phase is modeled by a Discrete Element Method (DEM) using a soft-sphere approach for the particle collision dynamic. Turbulence is included via a Large-Eddy approach using the Smagorinsky sub-grid model. The model takes into account detailed gas phase chemistry, zero-dimensional modeling of the pyrolysis and gasification of each individual particle, particle shrinkage, and heat and mass transfer between the gas phase and the particulate phase. We investigate the influence of wood feeding rate and compare exhaust gas compositions and temperature results obtained with the model against experimental data of a laboratory scale bubbling fluidized bed reactor.     

Gas flow in a bent channel

The results are given of experimental investigations of flow of gas (air) in a curvilinear cylindrical channel. Patterns of the streamlines near the wall and the separation region were obtained by blowing cold air through a transparent model. In an investigation of the flow of hightemperature gas, in which an electric arc heater was used to supply the thermal energy, the profiles of the total pressure and the stagnation temperature were measured at different sections of the channel. It was found that the deformation of the profiles after the bend ends earlier for the hot gas than for the cold. The heat flux increases sharply after the bend.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 154–157, September–October, 1981.I thank A. B. Vatazhin for helpful discussions.     

Convective heating of a blunt-nosed body in a nonuniform hypersonic gas stream

An investigation is made into the convective heating of a blunt-nosed body in an expanding stream of heated gas. The gas parameters at the outer edge of the boundary layer are determined on the basis of a solution obtained earlier by the authors [3]. Expressions are obtained which make it possible to convert the convective heat flux to a body in a uniform gas stream to one in a nonuniform stream. Dimensionless numbers are found and their influence on the convective heat flux to the body is investigated.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 127–133, July–August, 1981.     

Thermo-gravitational convection in a continuous optical discharge

The relative importance of such processes as the free convective motion of the gas, the absorption of the laser radiation and radiative heat transfer is discussed. The burning of a continuous optical discharge under experimental conditions [6] is theoretically investigated. The two-dimensional problem of the convective motion of the gas in an optical discharge burning in a vertical CO₂ laser beam inside a cylindrical chamber is solved. The principal characteristics of thermogravitational convection of the radiating air under conditions of local thermodynamic equilibrium at atmospheric pressure are studied on the temperature interval from 300 to 20 000°K.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 124–129, July–August, 1989.     

The behavior of a gas bubble in a shock wave

The phenomenon of thermal relaxation of the gas bubbles in a fluid behind a shock front is analyzed. The approach to solving the problem of heat transfer between a gas bubble and a fluid developed by the author is used to obtain a solution describing the initial stage of bubble collapse behind the shock front.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 187–189, September–October, 1993.