Flow Of Viscous Heat-conducting Gas Research Articles

Numerical investigation of flows with condensation in micronozzles

The paper considers the numerical simulation of the flow of argon with account for the condensation process in the micronozzle and behind it. To describe phase transitions, the initial mathematical model of viscous heat-conducting gas flow is supplemented with the equation of formation and growth of condensation nuclei in the flow. The developed mathematical model allows for simulating the process of gas condensation at low pressures and temperatures. It is shown that the condensate mass fraction in the flow is not less than 1% at the pressure and temperature of 5 bar and 200 K, respectively, when argon flows out of a micronozzle to the environment with the pressure of 0.01 Pa. At the nozzle exit, the size of condensed particles reaches 80 angstroms. The obtained results confirm the necessity to take into account the condensation phenomenon in micronozzle flows of inert gases.

Heat flux in supersonic flow past ballistic model at various angles of attack and wall temperatures

Supersonic flow of viscous heat-conducting gas around the ballistic model HB-2 and the resulting heat flux for M=3, angles of attack α=0°,8°,16°and various model surface temperatures were numerically studied using the compact version of the hyperbolic system of quasi-gasdynamic equations (CHQGD).Three-dimensional features of the flow structure and heat flux's dependence on the angle of attack and wall temperature were investigated. Longitudinal vortices on the model's leeward side near the symmetry plane were observed for α=16°. These flow separation regions significantly affect heat flux distribution on the model's leeward surface.

Simulation of a Spatial Flow in an Axisymmetric Nozzle with Nonsymmetrical Critical and Exit Sections

Using a conservative numerical method, a flow of viscous heat-conducting gas in the diffusor part of a spatial axisymmetric nozzle with a slanting exit section and partially overlapped critical section is simulated. The computations are carried out in a wide variation range of the parameters affecting the behavior and structure of the flow. The effect of the critical section’s area and pressure in the confusor part on the flow parameters in the diffusor part of the nozzle, position of flow separation points, and longitudinal and cross-sectional forces acting on the internal part of the nozzle is investigated. The distributions of the flow parameters in the nozzle are reported. The computations are carried out using parallel algorithms implemented on a computer system with a cluster architecture.

Exact Solutions to the Steady Navier–Stokes Equations of Viscous Heat-Conducting Gas Flow Induced by the Plane Jet Issuing from the Line Source

The plane stationary flow of viscous gas is considered, which is induced by the jet impacting the unbounded space and the domain between two diverging flat walls. Existence criteria of the Landau self-similar solutions are established for the source of gas flowing from the apex of a wedge with the thermally insulated walls and of wedge with the prescribed walls temperature. The analytical solutions are constructed in the case when the gas temperature is constant along the lines of flow and when the transfer coefficients are power functions of temperature.

Optimal control of a viscous heat-conducting gas flow

Under consideration is the problem of controlling the one-dimensional flow of a polytropic viscous heat-conducting ideal gas along an interval with a stationary boundary. The initial velocity and the velocity at the permeable stationary boundary are chosen as controls. We prove the existence of an optimal control, derive some necessary optimality conditions, and show that the solution set is compact.

Optimal control of a magnetohydrodynamic viscous heat-conducting gas flow

The control problem for a one-dimensional flow of a polytropic viscous heat-conducting perfect gas through an interval is considered. The density of external currents is taken as the control. The existence of an optimal control function is proved. Necessary optimality conditions are derived. The compactness of the set of solutions is established.

Effect of Volume Energy Supply on the Stability of a Subsonic Vortex Flow

Calculations of the stability of an axisymmetric vortex flow of viscous heat-conducting gas with volume energy supply are presented. The unperturbed axisymmetric vortex flow was found numerically using a quasi-cylindrical approximation of the Navier-Stokes equations under the assumption of constant peripheral-velocity circulation in the ambient co-current flow. The volume energy supply in the viscous vortex core was modeled by an additional source term in the energy equation. The stability characteristics of the viscous vortex flow in a longitudinal vortex with respect to both axisymmetric and non-axisymmetric three-dimensional waves traveling along the vortex axis and corresponding to both positive and negative values of the azimuthal wave number were found using the time-dependent formulation of the linear stability theory for compressible three-dimensional plane-parallel flows.

An efficient method for calculating viscous flows with a pronounced streamline curvature

In the present study, we propose a method based on the global iterations for the longitudinal component of the gradient of a function that specifies the transverse distribution of pressure. This method is algorithmically simpler [1] and requires approximately half as much memory and processor time for its computer realization. The efficiency of this method is illustrated by the computation of a viscous flow in the Laval nozzle where the gas flow is essentially subsonic at the inlet and supersonic at the outlet. The proposed method can be easily adapted to solving the problems of viscousgas aerodynamics. 1. Model of flow. We consider the second-order laminar flow of viscous heat-conducting gas in the planar or axially symmetric Laval nozzle. The set of smooth-channel equations [1] in the adapted system of coordinates ( ξ , η ) with respect to the natural variables has the following form:

Effect of volume energy supply on swirled flows in a subsonic cocurrent stream

The results of a numerical investigation of the effect of thermal energy supply on a swirling viscous heat-conducting gas flow in a subsonic cocurrent stream are presented. The initial stage of development of the swirling flow in the neighborhood of the vortex axis with constant circulation in the outer flow region is considered for two different distributions of the streamwise velocity vector component which simulate a swirling jet-type flow and a wake flow with a streamwise velocity deficit. The effect of local volume energy supply in the neighborhood of the vortex axis, the circulation of the azimuthal velocity component, and the longitudinal pressure gradient in the inviscid stream on the development of the swirling flow and the process of breakdown of cocurrent vortex flows is investigated.

Numerical investigation of supersonic viscous gas flow over long blunt cones with allowance for equilibrium physicochemical effects

Supersonic axisymmetric viscous heat-conducting gas flow over long spherically biunted cones is considered over a broad range of Reynolds numbers on the basis of the complete system of viscous shock layer equations. An economical numerical method based on global iterations is used to solve the viscous shock layer equations. The general influence of the second-approximation effects of boundary layer theory and the influence of equilibrium physicochemical processes on the heat loads are determined for bodies with a large aspect ratio.

Effect of surface temperature on the stability of the swept attachment line boundary layer

At fairly high Reynolds numbers instability may develop on the line of attachment of the potential flow to the leading edge of a swept wing and lead to a transition to boundary layer turbulence directly at the leading edge [1, 2]. Although the first results relating to the stability and transition of laminar flow at the leading edge of swept wings were obtained almost 30 years ago, the problem remains topical. The stability of the swept attachment line boundary layer was recently investigated numerically with allowance for compressibility effects [3, 4]. Below we examine the effect of surface temperature on the stability characteristics of the laminar viscous heat-conducting gas flow at the leading edge of a side slipping wing.

Sensitivity of a subsonic flow to oscillating effects localized at the base of the boundary layer

Three methods of exciting small oscillations in a subsonic viscous heat-conducting gas flow are investigated: vibration of part of the surface, periodic blowing-suction and oscillations of the wall temperature. The boundary-value problems formulated are calculated numerically for a linearized system of Navier-Stokes equations assuming parallelism of the main flow. The processes of sound and Tollmien-Schlichting wave generation are studied.

Formation of one-dimensional flows of viscous heat-conducting gas for small parameter perturbations

The formation of unsteady one-dimensional flows is studied, using the solution of the problem of reflection of a normally incident plane shock wave from a heat-conducting wall as an example. The process is considered for low intensities of the incident wave, behind which the gas temperature hardly differs from the initial wall temperature. The flows with complicated internal structures that arise are investigated on the basis of Navier-Stokes equations linearized near the initial state. An analytic solution of the problem describing the discontinuous structure of the reflected flow is constructed, which can serve as a test in the numerical solution of the original nonlinearized Navier-Stokes equations. The influence of the Prandtl numbers, the specific heat ratio, and dissipative and other factors is considered. The features of the effects of viscosity, thermal conductivity, and accommodation on the formation of flows and ideal (inviscid, nonheat-conducting) and dissipative zones are traced. It is shown that the solution of the linearized system agrees with the solution for asymptotic flow regimes.

A study of a finite-difference method for one-dimensional viscous heat-conducting gas flow equations. Part II: Error estimates and realization

A study of a finite-difference method for one-dimensional viscous heat-conducting gas flow equations. Part II: Error estimates and realization

Numerical modeling of intense heat release in a slow viscous gas flow

The pulsed heat release in an essentially subsonic flow of viscous heat-conducting gas in a plane channel is numerically modeled. The presence of two time scales makes it possible to calculate the initial stage of the gas dynamic process within the framework of the inviscid gas model. In this phase a monotonie difference scheme of second order of accuracy is employed. The description of the later stages of the process is based on the investigation of a system of equations obtained from the complete Navier-Stokes equations for a compressible gas on the assumption that the Mach number and the hydrostatic compressibility parameter are small. The results of the calculations are presented for the case of a rectangular channel.

Exact equations and transport coefficients for a multicomponent gas mixture with a partially ionized plasma

Molecular transport processes are governing in many problems associated with-the flow of high-temperature multicomponent gas mixtures. Thus, a flow with a partially dissociated and ionized multicomponent gas is realized in problem of viscous heat-conducting gas flow around bodies in practically the whole flow domain outside the bow shock on the most heatstressed section of the trajectory, where convective heat transfer predominates, during entry in the atmosphere of planets of the solar system. Molecular transport processes in such a mixture govern directly the molecular heat and mass fluxes, the viscous friction force, as well as the rate of thermochemical destruction of the streamlined surface [i]. Transport processes play an important role in the flow of a weakly ionized plasma in a MHD generator [2], gas-phase nuclear reactors [3], and other problems. Consequently, a sufficiently rigorous and complete study of the behavior of the transfer coefficients in a broad temperature and pressure range is a problem of practical importance, and even more so since experimental investigations of multicomponent plasmas at high temperatures are related to great complexities in the diagnostics. It is also important to note that a study of all the necessary properties of a complete set of transfer coefficients has not been performed up to now because of the complexity of the appropriate formulas given by the kinetic theory of gases in the exposition in [4]. Of the experimental papers, [5-7] should be noted, in which the investigation of certain transfer properties of air, nitrogen, hydrogen, and argon was performed (mainly the heat conduction and viscosity coefficients only). Numerical computations were carried out in [8-11] for the transport properties of ionized gases by kinetic theory methods [4] with high approximations taken into account in a polynomial expansion of the distribution functions in Sonin polynomials. However, for flows of chemically equilibrium hightemperature gases for which effective coefficients are introduced in the hydrodynamics equations with additional terms associated with component transfer, heat liberation in reactions, and the use of quasineutrality conditions of the ionized mixtures taken into account (a strict determination of the complete set of effective transfer coefficients is given in [12, 13]), computations of all the effective coefficients in the hydrodynamics equations have never been performed successively. Up to now there is not sufficient information in the literature about the influence of any coefficient in any element temperature, pressure, and concentration range, nor about the role of taking account of high approximation in the computation of the transport coefficients for determining the heat flux, the component diffusion fluxes, and the viscous friction force [14].