How Computational Grid Refinement in Three Dimensions Affects CFD-DEM Results for Psuedo-2D Fluidized Gas-Solid Beds

2017 ◽  
Author(s):  
Annette Volk ◽  
Urmila Ghia
Keyword(s):  
Three Dimensional ◽  
Computational Grid ◽  
Three Dimensions ◽  
Computational Grids ◽  
Grid Refinement ◽  
2D Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Bed Thickness ◽  
Simulation Results ◽  
Accuracy Of Results

Computational Fluid Dynamics (CFD)-Discrete Element Method (DEM) simulations are designed to model a pseudo-two-dimensional fluidized bed. Bed behavior and accuracy of results are shown to change as the simulations are conducted on increasingly refined computational grids. Trends of the results with grid refinement are reported for both three-dimensional, uniform refinement, and for grid refinement in only the direction of bed thickness. Pseudo-2D simulation results are examined against previously published experimental data to assess relative accuracy compared to fully 3D simulation results. Two drag laws are employed in the simulations, resulting in different trends of results with computational grid refinement. From these results, we present suggestions for accurate model design.

scholarly journals How Computational Grid Refinement in Three Dimensions Affects Computational Fluid Dynamics-Discrete Element Method Results for Psuedo-Two-Dimensional Fluidized Gas–Solid Beds

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Annette Volk ◽  
Urmila Ghia ◽  
Milind A. Jog
Keyword(s):  
Three Dimensional ◽  
Computational Grid ◽  
Computational Grids ◽  
Two Dimensional ◽  
Grid Refinement ◽  
Computational Cell ◽  
Bed Height ◽  
Study Results ◽  
Bed Thickness ◽  
Drag Law

Computational fluid dynamics (CFD)-discrete element method (DEM) simulations are designed to model a pseudo-two-dimensional (2D) fluidized bed, in which bed thickness is minimal compared to height and length. Predicted bed behavior varies as the simulations are conducted on increasingly refined computational grids. Pseudo-2D simulation results, in which a single computational cell spans the bed thickness, are compared against fully-three-dimensional (3D) simulations results. Both pseudo-2D and fully-3D simulations exhibit high accuracy when sufficiently refined. Indicators of bed behavior, such as bed height, bed height fluctuation, bubble generation frequency, and segregation, do not appear to converge as the cell size is reduced. The Koch-Hill and Gidaspow drag laws are alternately employed in the simulations, resulting in different trends of results with computational grid refinement. Grid refinement studies are used to quantify the change in results with grid refinement for both three-dimensional, uniform refinement, and for two-dimensional refinement on pseudo-2D computational grids. Grid refinement study results indicate the total drag converges as the computational grid is refined, for both 3D and pseudo-2D approaches. The grid refinement study results are also used to distinguish the relatively grid-independent results using the Koch-Hill drag law from the highly grid-dependent Gidaspow drag law results. Computational cell size has a significant impact on CFD-DEM results for fluidized beds, but the grid refinement study method can be used to quantify the resulting numerical error.

scholarly journals Optimization of the Turbulence Model on Numerical Simulations of Flow Field within a Hydrocyclone

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Yan Xu ◽  
Zunce Wang ◽  
Lin Ke ◽  
Sen Li ◽  
Jinglong Zhang
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Cross Sections ◽  
Three Dimensional ◽  
Reynolds Stress Model ◽  
Computational Grids ◽  
Test Results ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Simulation Results

Reynolds Stress Model and Large Eddy Simulation are used to respectively perform numerical simulation for the flow field of a hydrocyclone. The three-dimensional hexahedral computational grids were generated. Turbulence intensity, vorticity, and the velocity distribution of different cross sections were gained. The velocity simulation results were compared with the LDV test results, and the results indicated that Large Eddy Simulation was more close to LDV experimental data. Large Eddy Simulation was a relatively appropriate method for simulation of flow field within a hydrocyclone.

scholarly journals A 3D CFD model analysis of the hydraulics of an outfall structure at a power plant

2005 ◽  
Vol 7 (4) ◽  
pp. 283-290 ◽  
Author(s):  
Liaqat A. Khan ◽  
Edward A. Wicklein ◽  
Mizan Rashid
Keyword(s):  
Power Plant ◽  
Three Dimensional ◽  
Cooling Water ◽  
Computational Grid ◽  
Cfd Model ◽  
Practical Application ◽  
Complex Velocity ◽  
Near Surface ◽  
Circulation Patterns ◽  
Computational Fluid Dynamics Cfd

A practical application of a three-dimensional (3D) computational fluid dynamics (CFD) model to an outfall structure of a power plant is presented in this paper. The outfall structure, used for discharging 55 m3/s of cooling water to a reservoir, consists of two inflow pipes, two deflectors and a baffle wall. The computational grid, resolving all the geometric features of the outfall structure consists of 350,660 hexahedral cells. The CFD model was run for two configurations of the outfall structure, with and without a baffle wall. The interactions of two high velocity jets with deflectors and baffle wall create complex velocity distribution and circulation patterns. Initially, both the jets bifurcate and then merge as they propagate downstream. At the outlet, the maximum near-surface velocities are not significantly different for the two configurations of the outfall structure. However, when the baffle wall is used the near-bed velocities, responsible for reservoir bed scouring, are approximately 75% smaller.

scholarly journals Arbitrary Lagrange–Eulerian code simulations of turbulent Rayleigh–Taylor instability in two and three dimensions

2003 ◽  
Vol 21 (3) ◽  
pp. 455-461 ◽  
Author(s):  
S.V. WEBER ◽  
G. DIMONTE ◽  
M.M. MARINAK
Keyword(s):  
Linear Growth ◽  
Three Dimensional ◽  
Taylor Instability ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Grid Refinement ◽  
Group Code ◽  
Interface Reconstruction ◽  
Intercomparison Project ◽  
Rayleigh Taylor Instability

We have performed simulations of the evolution of the turbulent Rayleigh–Taylor instability with an arbitrary Lagrange–Eulerian code. The problem specification was defined by Dimonteet al.(2003) for the “alpha group” code intercomparison project. Perfect γ = 5/3 gases of densities 1 and 3 g/cm3are accelerated by constant gravity. The nominal problem uses a 2562× 512 mesh with initial random multiwavelength interface perturbations. We have also run three-dimensional problems with smaller meshes and two-dimensional (2D) problems of several mesh sizes. Under-resolution lowered linear growth rates of the seed modes to 5-60% of the analytic values, depending on wavelength and orientation to the mesh. However, the mix extent in the 2D simulations changed little with grid refinement. Simulations without interface reconstruction gave penetration only slightly reduced from the case with interface reconstruction. Energy dissipation differs little between the two cases. The slope of the penetration distance versus time squared, corresponding to the α parameter inh= αAgt2, decreases with increasing time in these simulations. The slope, α, is consistent with the linear electric motor data of Dimonte and Schneider (2000), but the growth is delayed in time.

A Thermohydrodynamic Analysis of Dry Gas Seals for High-Temperature Gas-Cooled Reactor

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Wang Hong ◽  
Zhu Baoshan ◽  
Lin Jianshu ◽  
Ye Changliu
Keyword(s):  
High Temperature ◽  
Film Flow ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Dry Gas Seal ◽  
Safety Requirements ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Gas Seals ◽  
High Temperature Gas

A comprehensive analysis method is proposed to resolve the problem of simulating the complex thermoflow with two kinds of distinct characteristic lengths in a dry gas seal. A conjugated simulation of the complicated heat transfer and the gas film flow is carried out by using the commercial computational fluid dynamics (CFD) software CFX. By using the proposed method, three-dimensional velocity and pressure fields in the gas film flow and the temperature distribution within the sealing rings are investigated for three kinds of film thickness, respectively. A comparison of thermohydrodynamic characteristics of the dry gas seal is conducted between the sealed gas of air and helium. The latter one is used in a helium compressor for a high-temperature gas-cooled reactor (HTGR). From comparisons and discussions of a series of simulation results, it will be found that the comprehensive proposal is effective and simulation results are reasonable. Even under a hypothetical accidental condition, the maximum temperature rise in the dry gas seal is within the acceptable range of HTGR safety requirements.

Compressing Aerodynamic Hazard Data

2022 ◽  
Author(s):  
Yang Zhou ◽  
Nicolas Boullé ◽  
David Barton ◽  
Eduard Campillo-Funollet ◽  
Cameron Hall
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Data Streaming ◽  
Compression Method ◽  
Simulation Data ◽  
Geometrical Features ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Compression ◽  
And Control

Data compression of three-dimensional computational fluid dynamics (CFD) simulation data is crucial to allow effective data-streaming for drone navigation and control. This problem is computationally challenging due to the complexity of the geometrical features present in the CFD data, and cannot be tackled by standard compression techniques such as sphere-tree. In this report, we present two different methods based on octree and cuboid primitives to compress velocity isosurfaces and volumetric data in three dimensions. Our volume compression method achieves a 1400 compression rate of raw simulation data and allows parallel computing.

scholarly journals Modelling of a passive autocatalytic hydrogen recombiner – a parametric study

Nukleonika ◽  
2015 ◽  
Vol 60 (1) ◽  
pp. 161-169 ◽  
Author(s):  
Antoni Rożeń
Keyword(s):  
Mass Transfer ◽  
Gas Flow ◽  
Model Comparison ◽  
Exothermic Reaction ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computational Grids ◽  
Flow Rates ◽  
Chemical Surface ◽  
Simulation Results

Abstract Operation of a passive autocatalytic hydrogen recombiner (PAR) has been investigated by means of computational fluid dynamics methods (CFD). The recombiner is a self-active and self-adaptive device used to remove hydrogen from safety containments of light water nuclear reactors (LWR) by means of a highly exothermic reaction with oxygen at the surface of a platinum or palladium catalyst. Different turbulence models (k-ω, k-ɛ, intermittency, RSM) were applied in numerical simulations of: gas flow, heat and mass transport and chemical surface reactions occurring in PAR. Turbulence was found to improve mixing and mass transfer and increase hydrogen recombination rate for high gas flow rates. At low gas flow rates, simulation results converged to those obtained for the limiting case of laminar flow. The large eddy simulation technique (LES) was used to select the best RANS (Reynolds average stress) model. Comparison of simulation results obtained for two- and three-dimensional computational grids showed that heat and mass transfer occurring in PAR were virtually two-dimensional processes. The effect of hydrogen thermal diffusion was also discussed in the context of possible hydrogen ignition inside the recombiner.

Heat Storage Performance of a Honeycomb Ceramic Monolith

2014 ◽  
Vol 7 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Xiaoni Qi ◽  
Yongqi Liu
Keyword(s):  
Fluid Dynamics ◽  
Thermal Process ◽  
Heat Storage ◽  
Three Dimensional ◽  
Regenerative Process ◽  
Flow Rates ◽  
Storage Performance ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Honeycomb Ceramic

Honeycomb ceramic is the key component of the regenerative system. The three-dimensional numerical model has been established for thermal process in honeycomb regenerator. The numerical simulation was performed using FLUENT, a commercial computational fluid dynamics (CFD) code, to compare simulation results to the test data. The regenerative process of a honeycomb ceramic regenerator was simulated under different conditions. The results under different flow rates, different flowing time, different materials and different wall thickness were investigated. The work in this paper provides a theory basis and guide to the exploitation and appliance of HTAC system and the results of the numerical calculation can be used as the foundation of engineering design. The results may be utilized for design of porous media reactors and process optimization.

Three-dimensional and nonlinear analysis of efficiency enhancement in the E × B drifting electron laser with a prebunched electron beam and a planar wiggler

2013 ◽  
Vol 79 (5) ◽  
pp. 739-749 ◽  
Author(s):  
B. MARAGHECHI ◽  
M. JOKAR ◽  
F. JAFARI BAHMAN ◽  
A. NAEIMABADI
Keyword(s):  
Electron Beam ◽  
Nonlinear Analysis ◽  
Free Electron ◽  
Free Electron Laser ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Efficiency Enhancement ◽  
Nonlinear Simulation ◽  
Simulation Results

AbstractA nonlinear simulation of the E × B drifting electron laser (DEL) and the free-electron laser (FEL), in three dimensions, is presented for a prebunched electron beam to study efficiency enhancement. For the planar wiggler with flat pole faces, prebunching considerably shortens the saturation length, which favors the DEL compared to the FEL. Operation of the DEL with the planar wiggler with parabolic pole faces was not found to be possible due to the modulation of the E × B drift by the wiggler. However, simulation results of the FEL with this type of wiggler are reported.

Comparative Study on Pressure Field of Hydrostatic Thrust Bearing with Different Recess Shapes

2014 ◽  
Vol 621 ◽  
pp. 431-436
Author(s):  
Xiao Dong Yu ◽  
Zhi Qiang Wang ◽  
Xiu Li Meng ◽  
Qi Hui Zhou ◽  
Yan Qin Zhang ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Comparative Study ◽  
Thrust Bearing ◽  
Pressure Field ◽  
Three Dimensional ◽  
Distribution Law ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Volume Method

A comparative study on pressure field of hydrostatic thrust bearing with sector recess, rectangular recess, ellipse recess and I-shaped recess is carried out in order to solve the deformation of the hydrostatic thrust bearing. The Finite Volume Method has been used to compute three-dimensional pressure field of gap oil film between the rotation worktable and the base. This study theoretically analyzes the influence of recess shape on the bearing pressure characteristic according to Computational Fluid Dynamics (CFD) and lubricating theory. It has revealed its pressure field distribution law. The simulation results indicate that an improved characteristic will be affected by recess shape easily. Through this method, the safety of a hydrostatic thrust bearing with different recesses can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design, lubrication, and experiment and deformation computation for hydrostatic thrust bearing.

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