Simulation of the turbulent mixing of a passive impurity in a jet mixer

Results of numerical simulation of the mixing of a turbulent jet with a cocurrent incompressible-fluid flow (Schmidt number Sc ≈ 1000) in a cylindrical channel of circular cross section (axisymmetric mixer) with the use of the standard k-ε turbulence model and different models for the averaged value of the mixture fraction and its variance have been given. For the problem of mixing of an inert passive impurity, two regimes of flow — the regime with the formation of a recirculation zone and that without its formation — have been considered. The formulated statistical model has been verified with the use of experimental data and results of calculation by large-eddy simulation. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 666–681, July–August, 2008.     

Analysis of the process of mixing of a passive impurity in a jet mixer

The experimental results for two regimes of mixing of a passive impurity in an axisymmetric jet mixer — the mixing of a turbulent jet and a cocurrent flow to form a recirculation zone behind the nozzle and an analogous mixing without the formation of a recirculation zone (Re_d = 10,000) — have been presented. The velocity field has been measured in the mixer cross sections at different distances from the nozzle (0.1 < x/D < 9.1) with a one-component Doppler laser anemometer, whereas the scalar field (concentration of the passive impurity) has been diagnosed by the laser-induced fluorescence method. Based on the scalar distributions obtained, the autocorrelation function and the integral scale have been computed, the form of the probability density function has been restored, and the distributions of the asymmetry and excess coefficients have been constructed. Visualization of flow in the mixer has been carried out. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 46–59, March–April, 2007.     

Calculation of the velocity of a plasma flow in the nozzle exit section of a coaxial-electrode Hall accelerator

The velocity of a plasma jet in the nozzle exit section and the pressure in the discharge zone of a coaxial-electrode Hall accelerator have been calculated on the basis of the experimentally measured enthalpy, temperature, and electron concentration near the indicated section within the framework of a model of the magnetic hydrodynamics of a plasma flow. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 102–108, May–June, 2006.     

Simulation of the internal dynamics of solid-fuel rocket engines on the basis of the STAR-CD suite

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. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 50–56, July–August, 2006.     

Modeling of Nonstationary Flow in the Ramjet Channel with a Distributed Pulse-Periodic Energy Supply

A study has been made of the influence of a pulse-periodic supply of energy that is equal to the energy released in combustion of hydrogen in air on the structure of supersonic flow in a channel of variable cross section, which models the ramjet duct. The flow has been modeled based on two-dimensional nonstationary gas-dynamics equations. Different regimes of flow depending on the configuration of the zones of energy supply and the excess-air coefficient have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 152–157, July–August, 2005.     

Nonstationary flow in the model channel of a ramjet engine in pulse-periodic energy supply

A study has been made of the influence of the pulse-periodic supply of energy that is equal to the energy released in the combustion of hydrogen in air on the structure of supersonic flow in a channel of variable cross section, modeling the duct of a ramjet engine. The flow has been modeled on the basis of two-dimensional nonstationary gas-dynamic equations. Different flow regimes have been obtained depending on the configuration of the zones of energy supply and the excess-air coefficients. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 464–469, May–June, 2008.     

Heat transfer in a horizontal coiled pipe in a transient regime and at a near-critical pressure of a fluid

It has been established that in the region of pressures close to a critical one, heat transfer in a transient regime of motion of a single-phase flow in a horizontal coil pipe changes nonuniformly over the cross section of the perimeter. The main factors here are the influence of inertia forces and of free convection. Equations to calculate the heat-transfer coefficient are suggested. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 892–896, September–October, 2008.     

On the gas flow rate through a Mach disk in an underexpanded jet

An air jet with an excess static pressure at a regime of escape into quiescent air is considered. The range of Mach number variation is 1–3, and that of the inefficiency ratio 1–1000. An analysis has been made on the basis of the well-known experimental-calculated approximation dependences for stationary expanding flows. We solve the inverse problem where the parameters at the nozzle exit and the geometric characteristics of the initial section of the jet are known and it is required to find the remaining quantities corresponding to them. In the present analysis, this is the rate of flow through a central discontinuity and the integral characteristic of the magnitude of the total pressure loss. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 320–325, March–April, 2009.     

Instabilities of two-phase flows in short rectangular microchannels

Two-phase (liquid-gas) flows in a short horizontal slit channel of rectangular cross section with heights (thicknesses) from 100 to 500 μm have been experimentally studied using the laser-induced fluorescence and schlieren photography methods. It is established that the formation of various two-phase flow regimes and the transitions between different regimes are determined by instabilities of the liquid-gas flow in the side parts of a channel. In a 100-μm-thick channel, a frontal instability has been observed during the liquid-gas interaction in the region of liquid output from the nozzle.     

Analysis of mass-transfer phenomena in the dendritic net of solidifying steel ingots. 2. Convective diffusion of the impurity in the dendritic net of solidifying ingots

An analysis of the interaction of the melt flow with the surface of dendritic crystallites has been performed using the concept of a diffusion boundary layer, and the regularities of the impurity distribution over the cross section of ingots and castings in the process of their solidification have been revealed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 8–12, July–August, 2007.     

Flow structure of the active medium of a HF laser with a radially expanding nozzle unit

Measurements have been made of gasdynamic characteristics of the flow of the active medium as well as energy and spectral characteristics of radiation generated by a continuous chemical HF laser with a radially expanding nozzle unit. Based on the analysis of measurement results, the flow structure of the active medium has been determined, which is formed by the “nozzle–injector” reactant mixing scheme. It has been shown that only a part of the active medium is involved in the radiation generation. Measures for improving the efficiency of its use have been proposed.     

Conjugate heat transfer in a closed domain with a locally lumped heat-release source

Free convective heat transfer in a solution domain quite accurately modeling the cross section of the object of heat consumption has been investigated numerically. Typical velocity and temperature fields have been presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 56–63, January–February, 2006.     

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.     

Numerical and physical modeling of a low-velocity air flow in a channel with a circular vortex cell

Based on a numerical solution, by the finite-volume method, of two-dimensional Reynolds equations that are closed using Menter’s two-parameter turbulence model and on physical modeling in a wind tunnel the authors analyze flow in a channel with a cylindrical vortex cell of circular cross section. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 346–353, March–April, 2000.     

Heat transfer from tubes filled with a granular layer with account for its thermal anisotropy

The heat transfer from a tube filled with an infiltrated granular layer has been simulated with account for the parallel thermal conductivity of this layer at the first-kind and second-kind boundary conditions at the outer surface of the tube with the use of the Danckwerts conditions. Analytical dependences determining the influence of the parallel thermal conductivity of the granular layer on the average at its cross section as well as on the heat flow and the heat transfer in it have been obtained. Dependences for calculating the active length of a heat exchanger are presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 153–164, July–August, 2006.     

Formation of liquid drops in microchannels

A two-phase (liquid-gas) flow and the formation of liquid drops in a narrow horizontal slit channel of rectangular cross section with a height (thickness) of 100–440 μm has been experimentally studied. It is established that flow regimes exist in which drops can be formed at low values of reduced liquid and gas velocities. Various regimes are determined in which either immobile drops appear on the channel walls or moving drops are formed as a manifestation of instabilities in the two-phase flow.     

Instability of a two-phase flow in a rectangular channel

A two-phase (liquid-gas) flow in a short horizontal slit channel of a rectangular cross section with a height of 440 μm has been experimentally studied using a fluorescent method, which allowed the flow pattern to be monitored and its quantitative characteristics to be measured. It is established that two-phase flow regimes in this channel substantially differ from the classical regimes of flow in extended channels of large cross section. It is demonstrated that the formation of various two-phase flow regimes and the transitions between them in short narrow rectangular slits are determined by instability of the liquid-gas flow at the side-walls of the channel.     

Comparative Analysis of the Vortex Heat Exchange in Turbulent Flows around a Spherical Hole and a Two-Dimensional Trench on a Plane Wall

The vortex heat exchange in turbulent flows around a spherical hole and a transverse trench, identical in depth and in the shape of the middle cross section, on a plane wall has been numerically investigated using multiblock computational technologies. A factorized, implicit multiblock algorithm and a Menter's model of shear-stress transfer were tested in the process of comparative analysis of calculation and experimental data on flows around isolated holes. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 117–128, July–August, 2005.     

Filtration of a gas-condensate mixture near the hydraulic fracture

The problem of filtration of a gas-condensate mixture near the operating well with a hydraulic fracture has been investigated. It was assumed that flow is three-dimensional in the matrix and two-dimensional on the fracture. It has been shown that for steady-state flow, the problem is split into a purely physicochemical problem on phase transitions and a nonlinear partial boundary-value problem for the pressure field. An example of numerical solution for the fracture with a prescribed conductivity field has been given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 409–416, May–June, 2008.     

Distinctive features of filtration in a granular bed near the wall

A generalization of the Brinkman equation to the case of linear filtration has been proposed based on an analysis of the existing models of filtration of a liquid (gas) in a stationary granular bed. It has been shown that, with allowance for the local-porosity distribution over the cross section of the apparatus, this equation makes it possible to describe velocity distributions observed experimentally in the wall zone. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 141–147, September–October, 2007.