Gas-dispersed Flow Research Articles

A mathematical model of liquid motion in the gas dispersed flow of rotary mass transfer machine

The article includes the results of theoretical studies of motion dispersed liquid flow in countercurrent gas-liquid flow of mass transfer rotary machine. Dependences for calculating the trajectory of the drops in the rotor are obtained. The comparison of theoretical results with experimental data shows the adequacy of the obtained mathematical model

Simulation of fine-dispersed turbulent flow in a pipe on the basis of the nonlinear model of turbulent viscosity

A nonlinear model of turbulent viscosity (the explicit algebraic Reynolds stress model) for gas-dispersed flow with small heavy particles has been presented. The calculations have been checked by comparison with the experimental data on the effect of the fine-dispersed admixture on turbulent flow of air in a pipe.

Analysis of statistical model of heat transfer of particles in isotropic turbulence with constant temperature gradient

Comparison with the data of direct numerical calculations in isotropic turbulence with constant temperature gradient is used for verifying the statistical model of heat transfer in gas-dispersed turbulent flows. Analysis is made of the effect of thermal inertia of particles on the correlations between turbulent heat fluxes and intensities of temperature fluctuations in the dispersed and continuous phases.

Development and application of a diffusion-inertia model for simulating gas-dispersed turbulent flows

The development and application of a diffusion-inertia model are shown for computing the propagation and deposition of aerosol particles in turbulent flows. Comparison with experimental and numerical results points to the fact that the developed model adequately describes all the typical peculiarities of the process of the sedimentation of aerosol particles in straight and curved pipes.

Properties of erosive discharge in a gas-dispersion flow

Erosive discharge in the flow of a gas-dispersion mixture (air with dispersed microscopic drops of an electrolyte) has been experimentally studied. The products of erosion were obtained by coating the electrodes with a wax (this method was originally used by N. Tesla). Two phenomena were observed behind the discharge gap, i.e., (i) a linear breakdown in the form of a bead lightning (within 0.5–1 m behind the interelectrode gap) and (ii) the appearance of long-lived plasma formations (plasmoids). Cotton-like wax deposits formed on glass slides were examined in optical microscopes at various magnifications. The propagation of long-lived plasmoids in an applied magnetic field was monitored by a high-speed TV camera. Waveforms of a current transferred by the gas-dispersion flow were measured using a conducting screen. Based on these data, a self-consistent physical model is formulated, which describes the generation, evolution, and decay of the long-lived plasmoids.

Erratum to: “Thermal stability of a gas-dispersed flow in a spray drier”

Erratum to: “Thermal stability of a gas-dispersed flow in a spray drier”

Use of the large-particle method for calculating three-phase flows in convergent channels

This study deals with applying the large-particle method to the flow of three-phase media in convergent channels (confusers). A hydrodynamic flow pattern is studied in a wide range of variation of determining parameters of an undisturbed flow. Special attention is paid to the modes of motion of gas-dispersed flows in curvilinear channels with the large mass content of a dispersed phase at the inlet of the confuser.

Thermal stability of a gas-dispersed flow in a spray drier

Thermal stability of a gas-dispersed flow in a spray drier

Turbulent gas-dispersed flow in a pipe with sudden expansion: numerical simulation

A mathematical model was developed to simulate two-phase gas-dispersed flow moving through a pipe with axisymmetric sudden expansion. In the model, the two-fluid Euler approach was used. The model is based on solving Reynolds-averaged Navier — Stokes equations for a two-phase stream. In calculating the fluctuating characteristics of the dispersed phase, equations borrowed from the models by Simonin (1991), Zaichik et al. (1994), and Derevich (2002) were used. Results of a comparative analysis with previously reported experimental and numerical data on two-phase flows with separation past sudden expansion in a plane channel and in a pipe are given.

Two approaches to closing the equations of momentum and heat transfer in turbulent chemically reactive gas-dispersed flows on the stabilized portion of an axisymmetric channel

Consideration is given to two systems of equations of transfer of correlations of particle-velocity and temperature pulsations, which differ in the method of closing. A closed description of the heat transfer of the solid phase is carried out at the level of equations for second moments in the first case and for third moments in the second case. A comparative analysis of the two methods of calculation of the ascending nonisothermal flow of a gas suspension is made based on numerical investigations.

Modeling of the rotational motion of a dispersed phase using the equations of transfer of the second and third moments of pulsations of the translational and angular velocities of particles

This article considers the Eulerian continuum description of turbulent transfer of momentum and moment of momentum in a solid phase on the basis of the equations of transfer of the second and third moments of pulsations of the linear and angular velocities of particles. The pulsating characteristics of a gas are computed using the two-parameter model of turbulence generalized to the case of gas-dispersed turbulent flows.

Modelling of local admixture stratification in in disperse flows with kinematic singularities

Development of mesoscale non-uniformities of the dispersed phase in dusty-gas flows with kinematic singularities is considered. As examples, the following flows with dispersed admixture are studied: a flow near a stagnation point of two colliding viscous streams, gas-dispersed flow near a rigid wall, flows with localized vorticity, an unsteady flow in a neighborhood of a zero acceleration point.

Inertial Settling of Particles from a Gas-Dispersed Flow on a Curvilinear Surface

Consideration is given to problems of settling of particles of a dispersed impurity from a subsonic jet flow on a curvilinear surface. Flow of the carrier medium is modeled based on the equations of vortex flow of a nonviscous incompressible liquid; they are written in the stream function-velocity vortex variables. The interaction of plane and round jets with obstacles of different shapes for the zero and nonzero initial vorticities of the flow is modeled numerically. The coefficient of sedimentation of the impurity is calculated as a function of the particle size and the obstacle shape.

Influence of Turbulence on the Deposition of Particles from a Gas-Dispersed Flow on the Wall

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.

Stochastic Modeling of Impurity Motion and Scattering in the Mechanics of Turbulent Gas-Dispersed Flows

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.

Regional Mean Bubble Diameters and Gas Holdup in Agitated Gas-Liquid Contactors

Gas-liquid contacting in mechanically agitated vessels is widely used in the process industry. Bubble size measurements at different flow regions in the vessel provide useful information for the mechanisms of gas dispersion and gas-liquid flow. In this work, bubble size distributions and distributions of Sauter mean bubble diameters at four different regions in air-water and air-NaCl solution systems agitated by a six-blade disk turbine are measured by using the photographic method. The effects of gassing rate, impeller speed and electrolyte presence in the system have been examined.

MODELLING OF RELEASE OF GAS FROM HIGH-PRESSURE PIPELINES

SUMMARY The problem investigated is the break of a high-pressure pipeline carrying natural single-phase gas which may condensate (retrograde) when the pressure drops. Single-phase non-ideal gas is assumed using a generalized equation of state. Taking advantage of the choked massflow condition, the break is split into a pipe flow problem and a dispersion flow problem, both solved using a finite difference control volume scheme. The transient flow field from the pipeline break location is expanded analytically, using an approximation of the governing equations, until ambient pressure is reached and matched to the corresponding gas dispersion flow field using as subgrid model a jet box with a time-varying equivalent nozzle area as an internal boundary of the dispersion domain. The turbulence models used for the pipe and dispersion flow fields are an empirical model of Reichard and the k-* model for buoyant flow respectively. The pipe flow simulations indicate that the flow from the pipeline might include dispersed condensate which will affect quantitatively the mass flow rate from the pipeline and qualitatively the gas dispersion if the condensate rains out. The transient dispersion simulation shows that an entrainment flow field develops and mixes supersaturated gas with ambient warmer air to an unsaturated mixture. Because of the inertia of the ambient air, it takes time to develop the entrainment flow field. As a consequence of this and the decay of the mass Aow with time, the lower flammability limit of the gasair mixture reaches its most remote downstream position relatively early in the simulation (about 15 s) and withdraws closer to the break location.

Calculation of two-phase swirling flows

The results of calculating the diffusion of a dispersed admixture in turbulent swirling jet flows using the model of momentum transfer in a turbulent gas—dispersion flow proposed by the authors are presented. These results are compared with experimental data and with calculations based on various mathematical models.

A diffusion-migration model for separation of a finely dispersed impurity

Calculations of the separation process of a dispersed phase in centrifugal apparatuses are performed using a diffusion-migration approximation to describe a turbulent gas dispersed flow. Comparison is made of various models for the description of the finely dispersed impurity separation.

Modeling of the particle dynamics in the wall region of turbulent gas dispersion flow

Modeling of the particle dynamics in the wall region of turbulent gas dispersion flow