scholarly journals Numerical Investigation of the Effect of Bottom Shape on the Flow Field and Particle Suspension in a DTB Crystallizer

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Hao Pan ◽  
Jun Li ◽  
Yang Jin ◽  
Bo Yang ◽  
Xing Li
Keyword(s):  
Flow Field ◽  
Volume Fraction ◽  
Fluid Model ◽  
Bottom Surface ◽  
Particle Suspension ◽  
Eulerian Model ◽  
Surface Diameter ◽  
Computational Fluid Dynamics Cfd ◽  
Two Fluid Model ◽  
Two Fluid

The influence of the bottom shape on the flow field distribution and particle suspension in a DTB crystallizer was investigated by Computational Fluid Dynamics (CFD) coupled with Two-Fluid Model (Eulerian model). Volume fractions of three sections were monitored on time, and effect on particle suspension could be obtained by analyzing the variation tendency of volume fraction. The results showed that the protruding part of aWtype bottom could make the eddies smaller, leading to the increase of velocity in the vortex. Modulating the detailed structure of theWtype bottom to make the bottom surface conform to the streamlines can reduce the loss of the kinetic energy of the flow fluid and obtain a larger flow velocity, which made it possible for the particles in the bottom to reach a better suspension state. Suitable shape parameters were also obtained; the concave and protruding surface diameter are 0.32 and 0.373 times of the cylindrical shell diameter, respectively. It is helpful to provide a theoretical guidance for optimization of DTB crystallizer.

scholarly journals Computational investigation of liquid-solid slurry flow through an expansion in a rectangular duct

2014 ◽  
Vol 62 (3) ◽  
pp. 234-240 ◽  
Author(s):  
Gianandrea Vittorio Messa ◽  
Stefano Malavasi
Keyword(s):  
Volume Fraction ◽  
Particle Density ◽  
Fluid Model ◽  
Solid Volume Fraction ◽  
Solid Particles ◽  
Rectangular Duct ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Two Fluid Model ◽  
Two Fluid

Abstract The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery

scholarly journals Behaviour and Stability of the Two-Fluid Model for Fine-Scale Simulations of Bubbly Flow in Nuclear Reactors

2015 ◽  
Vol 13 (4) ◽  
pp. 449-459 ◽  
Author(s):  
Henrik Ström ◽  
Srdjan Sasic ◽  
Klas Jareteg ◽  
Christophe Demazière
Keyword(s):  
Volume Fraction ◽  
Nuclear Reactors ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Domain Size ◽  
Fuel Assemblies ◽  
Two Fluid Model ◽  
Liquid Flows ◽  
Two Fluid ◽  
Meso Scale

Abstract In the present work, we formulate a simplistic two-fluid model for bubbly steam-water flow existing between fuel pins in nuclear fuel assemblies. Numerical simulations are performed in periodic 2D domains of varying sizes. The appearance of a non-uniform volume fraction field in the form of meso-scales is investigated and shown to be varying with the bubble loading and the domain size, as well as with the numerical algorithm employed. These findings highlight the difficulties involved in interpreting the occurrence of instabilities in two-fluid simulations of gas-liquid flows, where physical and unphysical instabilities are prone to be confounded. The results obtained in this work therefore contribute to a rigorous foundation in on-going efforts to derive a consistent meso-scale formulation of the traditional two-fluid model for multiphase flows in nuclear reactors.

Analysis of Powder Segregation in Powder Injection Molding

2011 ◽  
Vol 217-218 ◽  
pp. 1372-1379
Author(s):  
Yu Hui Wang ◽  
Xuan Hui Qu ◽  
Wang Feng Zhang ◽  
Yan Li
Keyword(s):  
Fluid Flow ◽  
Injection Molding ◽  
Volume Fraction ◽  
Fluid Model ◽  
Powder Injection Molding ◽  
Powder Injection ◽  
Exchange Term ◽  
Mixture Density ◽  
Two Fluid Model ◽  
Two Fluid

The powder injection molding (PIM) combines the thermoplastic and powder metallurgy technologies to manufacture intricate parts to nearly shape. The powder segregation is a special effect arising in PIM different from than the pure polymer injection. The two-fluid flow model is used to describe the flows of binder and powder so as to realize the prediction of powder segregation effect in PIM injection. To take into account binder–powder interaction, the mixture model of inter-phase exchange term is introduced in the two-fluid model. The two-fluid equations largely resemble those for single-fluid flow but are represented in terms of the mixture density and velocity. The volume fraction for each dispersed phase is solved from a phase continuity equation. As the key to calculate the phase exchange term, the drag coefficient is defined as a function of mixture viscosity. The effective viscosity of binder and powder are agreed with the additive principle. The volume fractions of binder and powder give directly the evolution of segregation during the injection course. Segregation during PIM injection was simulated by software CFX and results were compared with experimental data with good agreement. The basic reasons that caused segregation are identified as boundary effect, differences in density and viscosity of binder and powder. The segregation zones are well predicted. This showed that the two-fluid model is valid and efficient for the prediction of the segregation effects in PIM injection.

Evaluation on the Application of Two-Fluid Multiphase Model to Supercavity

2013 ◽  
Vol 275-277 ◽  
pp. 417-428
Author(s):  
Jing Jun Zhou ◽  
Chun Peng Dong ◽  
Qing Rui Xiang
Keyword(s):  
Flow Field ◽  
Fluid Model ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Multiphase Model ◽  
Structure Of Flow ◽  
Natural Cavitation ◽  
Two Fluid Model ◽  
Ventilated Supercavity ◽  
Two Fluid

The lubrication of external liquid with supercavity has been the goals of specialists for many years. Either ventilated cavity or natural cavity is firstly related to multiphase flow. In this paper, in order to quantitatively predict the cavitating flow especially the ventilated supercavity and understand the structure of flow field in the cavity, two kinds of multiphase model including the homogeneous flow model and the two-fluid model were adopted separately. Besides, SST and DES turbulence model are used for steady and unsteady simulations. By comparing the simulating results with experimental results in water tunnel, the two-fluid model was proved to have the high accuracy in predicting the ventilated supercavity including the cavity shape and lift coefficient of the vehicle. On the other hand, for natural cavitation, the mixture model and the two-fluid model have little difference in predicting the pressure coefficient, however, the two-fluid model can give more detailed flow field.

Numerical Simulation Analysis of Fluid in the Semi-State within the Desulphurization Tower

2010 ◽  
Vol 118-120 ◽  
pp. 921-924 ◽  
Author(s):  
Wei Lin Guo ◽  
Chao He
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Circulating Fluidized Bed ◽  
Simulation Analysis ◽  
Fluid Model ◽  
Simulation Design ◽  
Tower Structure ◽  
Two Fluid Model ◽  
Major Equipment ◽  
Two Fluid

In this paper, the flow field in the desulphurization tower is studied deeply based on two-fluid model, particle dynamics theory and FLUENT. A numerical simulation analysis of fluid within the desulphurization tower is done and the desulphurization tower is the major equipment in the system. The simulation design and calculations show that the two-fluid model is reasonable to analyze the flow field. The simulation results show that smoke can form good reaction environment within the desulphurization tower. It is meaningful for the further optimization of designing desulphurization tower structure in the circulating fluidized bed system.

scholarly journals On the use of α-shapes for the measurement of 3D bubbles in fluidized beds from Two-Fluid Model simulations

1970 ◽  
Vol 3 ◽  
pp. 26-27
Author(s):  
Ignacio Julián ◽  
David González ◽  
Javier Herguido ◽  
Miguel Menéndez
Keyword(s):  
Delaunay Triangulation ◽  
Fluidized Beds ◽  
Volume Fraction ◽  
Fluid Model ◽  
Accurate Description ◽  
Model Simulations ◽  
Two Fluid Model ◽  
Cloud Of Points ◽  
Two Fluid

A geometrical technique based on shape construction was employed to reconstruct the simulated domain of 3D bubbles in gas-solid fluidized beds from Two-Fluid Model simulations. The Delaunay triangulation of the cloud of points that represent volume fraction iso-surfaces was filtered using α-shapes, allowing a topologically accurate description of the bubbles.

scholarly journals Investigation on Bubble Diameter Distribution in Upward Flow by the Two-Fluid and Multi-Fluid Models

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5776
Author(s):  
Yongzhong Zeng ◽  
Weilin Xu
Keyword(s):  
Experimental Data ◽  
Volume Fraction ◽  
Fluid Model ◽  
Bubble Diameter ◽  
Diameter Distribution ◽  
Bubble Flow ◽  
Calculation Results ◽  
Two Fluid Model ◽  
Gas Volume ◽  
Two Fluid

Bubble flow can be simulated by the two-fluid model and the multi-fluid model based on the Eulerian method. In this paper, the gas phase was further divided into several groups of dispersed phases according to the diameter by using the Eulerian-Eulerian (E-E) multi-fluid model. The diameters of bubbles in each group were considered to be the same, and their distributions were reorganized according to a specific probability density function. The experimental data of two kinds of bubble flow with different characteristics were used to verify the model. With the help of the open-source CFD software, OpenFOAM-7.x (OpenFOAM-7.0, produced by OpenFOAM foundation, Reading, England), the influences of the group number, the probability distribution function, and the parameters of different bubble diameters on the calculation results were studied. Meanwhile, the numerical simulation results were compared with the two-fluid model and the experimental data. The results show that for the bubble flow with the unimodal distribution, both the multi-fluid model and the two-fluid model can obtain the distribution of gas volume fraction along the pipe radius. The calculation results of the multi-fluid model agree with the experimental data, while those of the two-fluid model differ greatly from the experimental data, which verifies the advantage of the multi-fluid model in calculating the distribution of gas volume fraction in the polydisperse bubble flow. Meanwhile, the multi-fluid model can be used to accurately predict the distribution of the parameters of each phase of the bubble flow if the reasonable bubble diameter distribution is provided and the appropriate interphase force calculation model is determined.

A Two-Fluid Model of Mixing in a Two-Dimensional Enclosure

1998 ◽  
Vol 120 (1) ◽  
pp. 115-126 ◽  
Author(s):  
O. J. Ilegbusi ◽  
M. D. Mat
Keyword(s):  
Potential Energy ◽  
Buoyancy Force ◽  
Volume Fraction ◽  
Fluid Model ◽  
Two Dimensional ◽  
Material Interface ◽  
Thermal Buoyancy ◽  
Two Fluid Model ◽  
Nonisothermal Conditions ◽  
Two Fluid

Mixing of fluids in a cavity under isothermal and nonisothermal conditions is studied with a two-fluid model. This model involves the solution of separate transport equations for zone-averaged variables of each fluid with allowance for interface transport of momentum and energy. The effects of thermal and potential energy driven convection as well as Prandtl number are investigated. The material interface is represented by the contour of the volume fraction separating the fluids. The effect of the buoyancy force due to the initial potential energy of the fluids is found to predominate over thermal buoyancy for comparable Grashof numbers.

3D Simulation of Flow in an Aeration Tank with Two Pipelines by a Two-Fluid Model

2012 ◽  
Vol 256-259 ◽  
pp. 2602-2605
Author(s):  
W.L. Wei ◽  
X.J. Zhao ◽  
Y. L. Liu
Keyword(s):  
Flow Model ◽  
Fluid Model ◽  
Flow Characteristics ◽  
Aeration Tank ◽  
Numerical Convergence ◽  
Model Combining ◽  
Computational Fluid Dynamics Cfd ◽  
Two Fluid Model ◽  
Volume Method ◽  
Two Fluid

In this paper, a numerical two-fluid flow model combining with the Realizable k–ε turbulent model for compressible viscous fluid is presented for the computation of flow characteristics in an aeration tank; and the equations are solved with the finite volume method. A multigrid technique based on the full approximation storage (FAS) scheme is employed to accelerate the numerical convergence. The numerical results for velocity and turbulent kinetic energy distribution in the aeration tank are obtained. It is shown that the Computational Fluid Dynamics (CFD) is a valuable tool to analyze the interaction of flow field and aeration.

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