Analysis of three-dimensional structures in complex turbulent flows

The basic integral relations used in analyzing various images of flows are given. The differences in the Abel transform for laminar and turbulent flows have been shown. The integral Uberoi–Kovasznay transform used in analyzing direct-shadow images of turbulent flows has been described. The present possibilities of digital laser speckle-photography for analyzing speckle-images of turbulent flows with the use of integral Erbeck–Merzkirch transforms have been analyzed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 8–17, January–February, 2009.     

Comparison of the results of modeling convective heat transfer in turbulent flows with experimental data

The results of simulation of natural turbulent convection in a square air cavity measuring 0.75 × 0.75 m and having isothermal vertical and highly heat-conducting horizontal walls are compared with the experimental data obtained for this cavity at a Rayleigh number equal to 1.58⋅10⁹. In carrying out numerical investigations, a two-dimensional, low-turbulence, two-parameter k–ε model known as the low-Reynolds-number k–ε turbulence model was used. The results of investigations are presented for the distributions of the velocity and temperature components, as well as local and average values of the Nusselt number. The model was also used in calculating forced turbulent convection in a low-velocity channel with a backward facing step. The results of modeling are compared with experimental data on heat transfer in a turbulent separation flow downstream of the step. In both cases, a satisfactory agreement of the measured values with those predicted by the k–ε turbulence model is obtained.     

Derivation and numerical solution of a closed equation for the specific isoscalar-surface area in a turbulent reactive flow

Based on the equation obtained earlier for the joint probability density function of the fluctuations of an isotropic turbulent scalar field of a reagent and its gradient[Inzh.-Fiz. Zh., 71, No. 5, 827–849 (1998)] the authors derived and numerically solved an equation for the specific isoscalar-surface area Σ_t(Γ) in a turbulent reactive flow. The equation for Σ_t(Γ) contains the single-point probability density function for pulsations of a reactive scalar and the time function that depend on the distribution of the energy of turbulent velocity pulsations and the intensity of scalar reagent pulsations by different length scales. The corresponding equations are written for all these functions. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 3, pp. 585–599, May–June, 2000.     

Dynamics of the viscous interaction of a ring vortex with a flat screen

A separation turbulent flow has been mathematically simulated on the basis of numerical solution of nonstationary Navier-Stokes equations for determining the dynamics of viscous interaction of a ring vortex with a flat screen. The problem was solved for an axisymmetric turbulent flow at Reynolds numbers falling within the range 10⁵–10⁷. On the basis of the calculation data obtained, the interaction of a ring vortex with a turbulent flow induced on the screen and with the secondary ring vortices was investigated. The data obtained are in qualitative agreement with the analogous data obtained by other authors with the use of the discrete-vortex method and the boundary-layer theory as well as with the available experimental and calculation data obtained for a laminar flow. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 1, pp. 184–190, January–February, 2008.     

On the calculation of turbulent fan jets

The self-similar equations for the dynamic and temperature fields of a forced free fan jet have been numerically integrated within the framework of the standard k-ε model of turbulence. The tables of solutions obtained for the velocity, temperature, and kinetic turbulent energy of the jet, as well as the mean square of the jet-temperature fluctuations at different turbulent Prandtl numbers, are presented. The quantitative parameters of the evolution of the average and turbulent characteristics of the jet flow were determined. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 1, pp. 62–67, January–February, 2008.     

Vortex effect as a consequence of negative turbulent diffusivity and viscosity

Conditions of the appearance of negative turbulent viscosity and diffusivity have been analyzed. The vortex effect has been explained on the basis of negative turbulent diffusivity as a result of the reverse of the cascade of turbulent energy transfer. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 112–117, September–October, 2006.     

Stochastic models of particle motion in a turbulent flow and their application for calculating internal flows

This paper considers issues connected with the construction and numerical realization of stochastic models of motion and scattering of condensed impurity particles in a turbulent flow based on the integration of a Langevin-type equation. The proposed model is used to calculate the turbulent flow of a low-concentration gas suspension in a channel with permeable walls. Calculations are performed for various values of the injection rate, sizes of particles, and the conditions of their introduction into the channel. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 3, pp. 136–147, May–June, 2007.     

Calculation of a turbulent monodisperse flow in an axisymmetric channel

A stationary isothermal model of the aerodynamics of a two-phase flow in an axisymmetric channel has been constructed with allowance for the turbulent and pseudoturbulent mechanisms underlying the transfer of the solid phase momentum. The equations of dispersed phase motion are closed at the level of the equations for the second moments of the pulsation velocities of particles, whereas the equation of momentum transfer of the carrier is closed on the basis of a one-parameter model of turbulence extended to the case of two-phase turbulent flows. The results of calculations are compared with experimental data. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 844–855, September–October, 2008.     

Turbulence in a Roughness Layer

Consideration is given to a model of turbulent flow in a roughness layer; the model is formed by the equations for turbulent momentum and turbulence-energy density and by free boundary conditions at self-establishing boundaries of the turbulent zone in the entire layer and in roughness cells. The model describes the interactions of the flow with the elements of roughness and the processes in the cells of different scales. Certain calculated characteristics of turbulence in vegetation are given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 143–151, July–August, 2005.     

Influence of heat and mass transfer on the development of two-dimensional separated flows

The effect of cooling and heating of a streamlined surface, free mass transfer, weak and strong isothermal injection, and suction on the development of supersonic turbulent separated flows is considered. The influence of the temperature factor and inefficiency ratio parameter on the gas-dynamic and geometric, characteristics of separated turbulent flows is estimated. Dnepropetrovsk State University, Dnepropetrovsk Institute of Chemical Engineering. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69,No. 4, pp. 647–656, July–August, 1996.     

Selection of applicability limits of a mathematical model of turbulence in formation of a steel ingot

Rational applicability limits of a turbulent model of momentum and heat transfer in a solidifying melt in an enclosure are determined based on multivariant calculations of hydrodynamic and thermophysical processes during casting and solidification of steel ingots. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 45–49, January–February, 1997.     

Scattering of radiation in an anisotropic turbulent medium

Scattering of laser radiation on density fluctuations in propagation of radiation through an anisotropic turbulent medium is analyzed. It is shown that the deviation angles in turbulent gas flows at atmospheric pressure equal ∼10⁻⁵–10⁻⁴ rad and can be detected by means of speckle photography. A statistical analysis of two-dimensional fields of deviation angles makes it possible to evaluate three-dimensional density correlation functions in a turbulent flow. It is shown that taking account of the turbulence anisotropy leads to distributions of the laser-radiation intensity over deviation angles that deviate substantially from the Gaussian distribution. Academic Scientific Complex “A. V. Luikov Institute of Heat and Mass Transfer of the National Academy of Sciences of Belarus,” Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 72, No. 1, pp. 96–101, January–February, 1999.     

Experimental and theoretical investigation of Taylor-Görtler instability in the boundary layer on a concave surface

Results of experimental and theoretical investigations of centrifugal instability in the turbulent boundary layer on a concave surface are presented. Linear and nonlinear regularities in the development of this type of instability are revealed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 2, pp. 279–283, March–April, 1997.     

Turbulent mixed convection in channels for different orientations of them in space

Investigations of heat transfer and turbulent transfer in mixed convection in tubes and plane channels for different orientations of them in space are reviewed. Lithuanian Power Institute, Kaunas. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 6, pp. 969–976, November–December, 1996.     

Negative turbulent heat conduction and its role in the formation of large-scale structures

A mechanism is proposed for the establishment of negative heat conduction under conditions of advanced turbulent convection, which leads to the formation of large-scale structures. A semi-empirical model of turbulent convection and experimental results are used to give some quantitative estimates. Pis’ma Zh. Tekh. Fiz. 24, 67–75 (April 26, 1998)     

Effect of the mode of flow in the initial boundary layer on the turbulence attenuation effect in a jet exposed to acoustic irradiation

Based on an analysis of experimental data on high-frequency acoustic excitation of turbulent jets, we investigate the effect of the mode of flow in the boundary layer of the outlet section of the nozzle on realization of the turbulence attenuation effect. It is claimed that high-frequency acoustic excitation of jets leads to a decrease in turbulent fluctuations on the axis of the initial stretch of the jet and to reduction of noise in both initially laminar and initially turbulent boundary layers at the nozzle outlet. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 1, pp. 81–85, January–February, 1998.     

Two-component radiation-gasdynamic model of a turbulent fireball

A two-dimensional computational model of the dynamics of a radiating turbulent fireball that can form in accident-induced explosion of a rocket at the launching position or in flight is presented. The model is based on the system of Navier-Stokes equations, two-component diffusion of explosion products (water vapor) in the ambient air, and a multigroup system of equations of thermal radiation transfer. The possibility of employing three models of turbulent mixing — the Prandtl model, the Penner-Haselman-Edwards model, and the Launder-Spalding model — is investigated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 31–38, January–February, 2000.     

Response of a pliable coating to turbulent pressure pulsations

The duration of the portions of coherence of turbulent pressure pulsations is determined experimentally. Based on this the dimensionless rate of deformation of the surface of a pliable coating is calculated with allowance for its inertial properties. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 4, pp. 712–718, July–August, 2000.