Search

Numerical modeling of the turbulent flow and conjugate heat exchange in a cavity bounded by a rotor and a stator is carried out. Coupled thermal calculations are based on the unsteady heat-conduction equation describing the temperature distribution within a solid and Reynolds-averaged Navier-Stokes equations closed using the k-ε turbulence model, which allow calculation of the velocity, pressure, and temperature distributions in the fluid-filled region. The space-time distributions of the temperature and the heat flux on the metal-fluid interface are obtained in two- and three-dimensional formulations of the problem on a structured and an unstructured grid. [ABSTRACT FROM AUTHOR]

Large eddy simulation is performed of a subsonic nonisothermal turbulent jet flowing out from a round nozzle into submerged space. The Navier-Stokes equations filtered over space and the RNG model of subgrid-scale viscosity are used for describing the flow. The calculations are performed for different values of the degree of jet preheating. The processing of the results of numerical simulation enables one to obtain the distributions of correlation moments of fluctuations of density, velocity, and temperature along the axis and in cross sections of jet flow. The calculation results are compared with the available data obtained using the solution of Reynolds-averaged Navier-Stokes equations and equations of the k-ɛ model of turbulence, as well as with the data of physical experiment. [ABSTRACT FROM AUTHOR]

This paper considers the influence of the mass flow of the gas ingested from the cavity formed by the rotor-to-stator clearance on the formation and structure of secondary flows in the blade passage of the gas-turbine stage. The flow is described by the Reynolds-averaged Navier-Stokes equations, to close which the Spalart-Allmaras model and the k-ε model of turbulence with corrections for the rotation and curvature of the streamlines are used. Comparison of the results of the numerical simulation obtained from the point of view of different turbulence models is made. [ABSTRACT FROM AUTHOR]

Turbulent flows in channels with intense distributed injection are modeled using the large eddy method and the two-equation k- ɛ turbulence model. The calculations are carried out for different velocities of injection from the channel walls. For a channel with one-sided injection the results of large eddy simulation are in good agreement with the measured data, whereas the calculations in accordance with the k- ɛ model give a less convex cross-sectional velocity profile and an appreciable error in determining the surface friction coefficient on the impermeable wall and also have certain other shortcomings. In the case of two-sided injection, the results of the calculations by the large eddy method and the k- ɛ model are in good agreement with one another and the data of physical experiments. [ABSTRACT FROM AUTHOR]

A simulation of the flow in a jet has been carried out with the use of the Reynolds-averaged, space-filtered Navier-Stokes equations closed by the k-ε model of turbulence and the subgrid RNG model of eddy viscosity. The results of calculations carried out on the basis of the k-ε model and the results of simulation of large vortices are in quantitative and qualitative agreement with the corresponding measurement data, which is evidence in favor of the main laws defining the decay of the gas-dynamic behavior of cold-gas submerged jets and the fluctuations of their parameters. [ABSTRACT FROM AUTHOR]

Large-scale eddies and related aerooptic effects in a turbulent boundary layer, free mixing layer, and a jet flowing out of a round nozzle into a submerged space are simulated. The results obtained are used to analyze the distortions produced in the phase function of a coherent light beam by the turbulent fluctuations of the parameters of the medium. The results of numerical calculation are compared with the data of natural experiment and data obtained by solving Reynolds-averaged Navier-Stokes equations. [ABSTRACT FROM AUTHOR]

Modeling of a turbulent flow in a cylindrical solid propellant charge channel having a circular recess (compensator) has been performed. Different variants of the compensator position and connection to the channel are discussed. The influence of the geometric and consumption factors on the formation of distributions of the gas-dynamic parameters and characteristics of turbulence in the working region has been investigated. [ABSTRACT FROM AUTHOR]

Unsteady-state heat transfer is considered in the region of interaction between a round turbulent jet and a normally positioned flat obstacle. The Navier-Stokes equations filtered over space are closed by the RNG-model of eddy viscosity which takes into account the curvature of the lines of flow in the region of turning of flow. The calculations are performed for different relative distances from the nozzle exit section to the obstacle and for different values of Reynolds number. The correlation between the distribution of characteristics of heat transfer over the obstacle surface and the eddy structure of the jet is discussed. [ABSTRACT FROM AUTHOR]

The total-pressure loss in gas turbines is evaluated. Reynolds-averaged Navier-Stokes equations are used for numerical calculations. The Spalart-Allmaras model, the k-ε model, and the two-layer model and their different modifications allowing for the rotation of the flow and the curvature of streamlines are used to close these equations. The role of different corrections to the turbulence models for the accuracy of calculated estimates is elucidated. [ABSTRACT FROM AUTHOR]

The characteristic features of the formulation of a two-layer turbulence model and its application in calculation of near-wall turbulent flows are considered. Factors that influence the effectiveness of implementation of the model and ways of expanding the limits of its applicability are discussed. The possibilities of the two-layer model are demonstrated by calculating a boundary layer on a flat plate with a longitudinal pressure gradient. A comparison of the results of calculation of the heat-transfer characteristics by the two-layer model, two-parameter dissipation model, and Spalart-Allmaras model with the data of a physical experiment and available correlations is made. [ABSTRACT FROM AUTHOR]

Velocity and concentration distributions of the condensed phase have been obtained based on the parameter-expansion method. The characteristics of two-phase flows in channels with strong and weak injections have been investigated. The factors exerting an influence on the velocity of nonequilibrium phase motion have been determined; the range of applicability of the solution obtained has been established and its qualitative behavior has been elucidated; the possibility of applying such a solution to calculation of the concentration of the condensed phase has been shown. [ABSTRACT FROM AUTHOR]

Flows in the channels of solid-fuel charges with cross sections having different views in plan and flows in the prenozzle volume and the nozzle unit of a solid-fuel rocket engine have been simulated on the basis of the STAR-CD suite for different types of charges and different designs of the input part of the engine nozzle. The influence of the compressibility, turbulence, geometric factors, and flow rate on the distributions of gasdynamic parameters in the working region of the engine has been investigated. [ABSTRACT FROM AUTHOR]

The accuracy and computational efficiency are compared for a number of models of subgrid eddy viscosity (Smagorinsky model, renormalization group model, and dynamic and one-parameter models). Space-filtered Navier-Stokes equations are solved numerically by the control-volume approach on a nonuniform grid with the use of high-resolution schemes in time and space. The numerical data are compared with the results of a physical experiment and direct numerical simulation. [ABSTRACT FROM AUTHOR]

The effect of longitudinal pressure gradient and localized injection on turbulent heat transfer on a flat plate is treated. The variation of the flow pattern, characteristics of heat transfer, and the efficiency of cooling the plate are investigated depending on the magnitude and sign of the pressure gradient and on the parameters of injection. The calculation results obtained using different models of turbulence are compared with data of physical experiment and available correlations. [ABSTRACT FROM AUTHOR]

The mechanisms of formation of three-dimensional jet flows inside large-scale vortex structures in a closed cubic cavity have been considered. The vortex structure of an incompressible viscous-fluid flow in this cavity has been investigated using the qualitative theory of ordinary differential equations. Singular points and their types and positions were determined at different Reynolds numbers on the basis of numerical calculations. [ABSTRACT FROM AUTHOR]

The bifurcation of the lines of a viscous-fluid flow in a rectangular cavity with a moving cover has been investigated for different ratios between the sides of the cavity and different Reynolds numbers on the basis of the qualitative theory of dynamic systems. The critical parameters of the problem, at which the type of singular points changes, and other topological characteristics of a vortex flow in the indicated cavity have been determined and the corresponding bifurcation diagrams have been constructed. [ABSTRACT FROM AUTHOR]

Consideration is given to problems associated with modeling of the motion of a condensed particle in a channel with injection with allowance for the action of different force factors (the hydrodynamic-drag force, the Saffman lift force, and the thermophoresis force). From the results of the numerical modeling, the author draws conclusions on the degree of influence of different force factors on the pattern of motion of the particle. [ABSTRACT FROM AUTHOR]

Issues associated with the development and realization of stochastic models of the impurity particle motion and scattering in a turbulent flow are considered. The proposed model is used to calculate turbulent flows of a low‐concentration gas suspension in channels and jets. We compare the results of the calculations obtained from the viewpoint of different models and the results of numerical simulation with the data in which the influence of turbulent pulsations on the particle motion was ignored. [ABSTRACT FROM AUTHOR]

Simulation of the scattering and deposition of dispersed‐phase particles in the region of interaction of a turbulent flow with an obstacle is considered. The regimes and distinctive features of deposition of particles in the vicinity of a critical point are investigated under different conditions. The sedimentation coefficient of the impurity is calculated as a function of the parameters of unperturbed flow and the particle size. The results of the calculations are compared to the data obtained without allowance for the influence of the fluctuations of the carrier‐flow velocity on the motion of the impurity. [ABSTRACT FROM AUTHOR]

Models of shock-wave processes induced by intense radiation fluxes in gas-disperse systems have been developed. The continuum coupling penetration model is used to simulate mixture motion. The problem of interaction of radiation with an individual particle is formulated to calculate source terms connected with the interphase mass, momentum, and energy transfer. Solution of a microproblem and of the problem of calculation of gasdynamic variables are found in parallel. Agreement of micro- and macrolevel problems ensured with the aid of iteration interrelationship in a computational procedure. Lengthwise distributions of mixture parameters and influence of different factors on the energy influx efficiency have been investigated. [ABSTRACT FROM AUTHOR]