scholarly journals DSMC Prediction of Particle Behavior in Gas-Particle Two-Phase Impinging Streams

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Min Du ◽  
Changsui Zhao ◽  
Bin Zhou ◽  
Yingli Hao
Keyword(s):  
Particle Concentration ◽  
Chemical Engineering ◽  
Lagrangian Approach ◽  
Particle Collision ◽  
Collision Rate ◽  
Two Phase ◽  
Particle Behavior ◽  
Transfer Processes ◽  
Collision Zone ◽  
Interparticle Collision

Devices with impinging streams have been employed in various fields of chemical engineering, as a means of intensifying heat and mass transfer processes. The particle behavior in gas-particle two-phase impinging streams (GPISs), which is of essential importance for the research of transfer processes, was simulated by an Eulerian-Lagrangian approach in this paper. Collisional interaction of particles was taken into account by means of a modified direct simulation Monte Carlo (DSMC) method based on a Lagrangian approach and the modified Nanbu method. A quantitative agreement was obtained between the predicted results and the experimental data in the literature. The particle motion behavior and the distributions of particle concentration and particle collision positions were presented reasonably. The results indicate that the particle distribution in GPIS can be divided into three zones: particle-collision zone, particle-jetting zone, and particle-scattering zone. Particle collisions occur mainly in the particle-collision zone, which obviously results in a few particles penetrating into the opposite stream. The interparticle collision rate and the particle concentration reach their maximum values in the particle-collision zone, respectively. The maximum value of the particle concentration increases with the increasing inlet particle concentration according to a logarithmic function. The interparticle collision rate is directly proportional to the square of local particle concentration.

Heat Transfer Processes in High-Temperature Flows of Two-Phase Media

2001 ◽  
Vol 32 (7-8) ◽  
pp. 7
Author(s):  
M. I. Osipov ◽  
K. A. Gladoshchuk ◽  
A. N. Arbekov
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Two Phase ◽  
Transfer Processes

scholarly journals Hydrodynamic Modeling of Turbulence Modulation by Particles in Swirling Gas-Particle Two-Phase Flow

2021 ◽  
Author(s):  
Yang Liu ◽  
Lixing Zhou
Keyword(s):  
Shear Stress ◽  
Two Phase Flow ◽  
Heavy Particle ◽  
Light Particle ◽  
Particle Collision ◽  
Order Moment ◽  
Enhancement Effect ◽  
Phase Flow ◽  
Primary Role ◽  
Two Phase

Abstract Turbulence modulations by particles of swirling gas-particle two-phase flow the axisymmetric chamber is investigated. To fully consider the preferential concentrations and anisotropic dispersions of particle, a second-order moment model coupling particle-particle collision model was improved based on the Eulerian-Eulerian two-fluid approach and the kinetic theory of granular flow. Proposed model, algorithm and in-house codes are validated and they are in good agreement with the experiment. Effects of ultralight expanded graphite and heavy Copper particles with large spans of Stokes number on gas velocity and fluctuations, Reynolds shear stress and tensor invariants, turbulence kinetic energy, and vortices structures are numerically simulated. Results show turbulent modulation exhibits strongly anisotropic characteristics and keeps in close relationship with flow structure. The disturbances of modulations, the alternations of vortex evolution are enforced by heavy-large particle with higher Stokes numbers. Preferential accumulations of light particle at shear stress regions in low vortices are weaker than those of heavy particle. For axial turbulence modulations, heavy particle plays the primary role on inhibition action due to larger inertia and light particle contributes to enhancement effect due to excellent followability.

scholarly journals The role of a mid-air collision in drifting snow

2018 ◽  
Author(s):  
Shuming Jia ◽  
Zhengshi Wang ◽  
Shumin Li
Keyword(s):  
Friction Velocity ◽  
Global Climate ◽  
Three Dimensional ◽  
Particle Collision ◽  
High Concentration ◽  
Three Dimensional Model ◽  
Two Phase ◽  
Drifting Snow ◽  
Collision Mechanism

Abstract. Drifting snow, a common two-phase flow movement in high and cold areas, contributes greatly to the mass and energy balance of glacier and ice sheets and further affects the global climate system. Mid-air collisions occur frequently in high-concentration snow flows; however, this mechanism is rarely considered in current models of drifting snow. In this work, a three-dimensional model of drifting snow with consideration of inter-particle collisions is established; this model enables the investigation of the role of a mid-air collision mechanism in openly drifting snow. It is found that the particle collision frequency increases with the particle concentration and friction velocity, and the blown snow with a mid-air collision effect produces more realistic transport fluxes since inter-particle collision can enhance the particle activity under the same condition. However, the snow saltation mass flux basically shows a cubic dependency with friction velocity, which distinguishes it from the quadratic dependence of blown sand movement. Moreover, the snow saltation flux is found to be largely sensitive to the particle size distribution since the suspension snow may restrain the saltation movement. This research could improve our understanding of the role of the mid-air collision mechanism in natural drifting snow.

Drop Coagulation in Cross-Over Pipe Flows of Wet Steam

1979 ◽  
Vol 21 (5) ◽  
pp. 357-360 ◽  
Author(s):  
J. J. E. Williams ◽  
R. I. Crane
Keyword(s):  
Drop Size ◽  
Chemical Engineering ◽  
Numerical Technique ◽  
Wet Steam ◽  
Coagulation Rate ◽  
Two Phase ◽  
Size Spectra ◽  
Pipe Flows ◽  
The Core ◽  
Median Diameter

A numerical technique is developed for predicting the evolution of drop-size spectra in turbulent, two-phase pipe flows. While relevant to many chemical engineering processes, it is applied here to the crossover pipes of a nuclear wet-steam turbine. Valid expressions for turbulent coagulation rate in the cross-over pipes are available only for drops below about 10 μm diameter in the core flow, and for those exceeding about 20 μm near the pipe wall. Using these expressions, it is found that the rapid formation of large drops in the core allows prediction for only a small fraction of the typical residence time in the pipe, but near the wall the volume median diameter of an initial 20 μm monodispersion can double in 100 ms. Further work is required to validate the technique and extend it to handle the intervening ranges of drop size and turbulence parameters.

scholarly journals Modeling of Interior Ballistic Gas-Solid Flow Using a Coupled Computational Fluid Dynamics-Discrete Element Method

2013 ◽  
Vol 80 (3) ◽  
Author(s):  
Cheng Cheng ◽  
Xiaobing Zhang
Keyword(s):  
Discrete Element Method ◽  
Gas Phase ◽  
Two Phase Flow ◽  
Discrete Element ◽  
Particle Collision ◽  
Contact Detection ◽  
Reconstruction Method ◽  
Phase Flow ◽  
Two Phase ◽  
Element Method

In conventional models for two-phase reactive flow of interior ballistic, the dynamic collision phenomenon of particles is neglected or empirically simplified. However, the particle collision between particles may play an important role in dilute two-phase flow because the distribution of particles is extremely nonuniform. The collision force may be one of the key factors to influence the particle movement. This paper presents the CFD-DEM approach for simulation of interior ballistic two-phase flow considering the dynamic collision process. The gas phase is treated as a Eulerian continuum and described by a computational fluid dynamic method (CFD). The solid phase is modeled by discrete element method (DEM) using a soft sphere approach for the particle collision dynamic. The model takes into account grain combustion, particle-particle collisions, particle-wall collisions, interphase drag and heat transfer between gas and solid phases. The continuous gas phase equations are discretized in finite volume form and solved by the AUSM+-up scheme with the higher order accurate reconstruction method. Translational and rotational motions of discrete particles are solved by explicit time integrations. The direct mapping contact detection algorithm is used. The multigrid method is applied in the void fraction calculation, the contact detection procedure, and CFD solving procedure. Several verification tests demonstrate the accuracy and reliability of this approach. The simulation of an experimental igniter device in open air shows good agreement between the model and experimental measurements. This paper has implications for improving the ability to capture the complex physics phenomena of two-phase flow during the interior ballistic cycle and to predict dynamic collision phenomena at the individual particle scale.

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