Fluidized beds modeling: Validation of 2D and 3D simulations against experiments

This paper reports on CFD simulations of freely bubbling gas fluidized beds using CFX-4, a commercial code developed by CFX Ltd. (formerly AEA Technology). Two Eulerian-Eulerian modelling approaches, the granular kinetic model and the particle-bed model (Gibilaro, 2001), have been investigated. The particle bed model has been recently implemented in CFX-4 for 2D simulations and a numerical procedure was developed to allow for a tight control of the fluid-bed voidage at maximum packing during the simulations, see Lettieri et al. (2003). The work has now been extended to 3D simulations and qualitative and quantitative results are presented in this paper for both the 2D and 3D simulations of the bubbling fluidization of a Geldart Group B material. Results on bed expansion, bubble size and bubble hold-up are reported. In particular, simulated bubble size is compared with predictions given by the Darton et al. (1977) equation at different bed heights. The paper shows that the bubble size predicted by both the granular kinetic model and the particle-bed model is in good agreement with the Darton's equation.

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3D Simulation of Surface Casing Cementing: Dispersion Effects

10.1115/omae2021-63338 ◽

2021 ◽

Author(s):

Ruizi Zhang ◽

Ian Frigaard

Keyword(s):

Computational Cost ◽

3D Models ◽

Interface Shape ◽

3D Simulations ◽

Numerical Studies ◽

Dispersion Effects ◽

Annular Gap ◽

Primary Cementing ◽

Other Regarding ◽

2D And 3D

Abstract Many numerical studies have been conducted regarding laminar miscible displacement flow in narrow, vertical, eccentric annuli. For the next decade it is likely that primary cementing flows on the scale of the well will continue to be simulated predominantly with 2D gap-averaged (2DGA) models. However, 3D simulations are less common due to the computational cost. The comparison between 2D and 3D models needs further attention, to understand the main discrepancies and thus help to understand primary cementing flows better. In this paper, comparisons of 3D against 2DGA model results show a range of interesting different phenomena, e.g. static layers, dispersive spikes, and instabilities. The predictions of the 2DGA model are the same as the 3D results to a degree. In particular, they are consistent with each other regarding the evolving process, interface shape, etc. However, the main difference with the 2DGA concentration arises from dispersion on the scale of the annular gap. From the recent research of Renteria and Frigaard (J. Fluid Mech., vol. 905, 2020) [1], a variety of dispersive effects are the main discrepancy between experiments and 2DGA results as well. We give representative examples of these flows in surface casing geometries and suggest methods for improvement of the 2DGA model.

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Experiment and multiphase CFD simulation of gas-solid flow in a CFB reactor at various operating conditions: Assessing the performance of 2D and 3D simulations

Korean Journal of Chemical Engineering ◽

10.1007/s11814-020-0646-7 ◽

2020 ◽

Vol 37 (12) ◽

pp. 2094-2103

Author(s):

Mukesh Upadhyay ◽

Myung Won Seo ◽

Parlikkad Rajan Naren ◽

Jong-Ho Park ◽

Thanh Dang Binh Nguyen ◽

...

Keyword(s):

Cfd Simulation ◽

Operating Conditions ◽

Solid Flow ◽

3D Simulations ◽

Multiphase Cfd ◽

2D And 3D

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Observable scattered light features from inclined and non-inclined planets embedded in protoplanetary discs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1649 ◽

2019 ◽

Vol 487 (4) ◽

pp. 5372-5387

Author(s):

Dylan L Kloster ◽

M Flock

Keyword(s):

Surface Density ◽

Scattered Light ◽

Intensity Variation ◽

Theoretical Models ◽

Upper Atmosphere ◽

High Mass ◽

Hydrodynamic Simulations ◽

3D Simulations ◽

2D And 3D ◽

Protoplanetary Discs

ABSTRACT Over the last few years instruments such as VLT/SPHERE and Subaru/HiCIAO have been able to take detailed scattered light images of protoplanetary discs. Many of the features observed in these discs are generally suspected to be caused by an embedded planet, and understanding the cause of these features requires detailed theoretical models. In this work we investigate disc–planet interactions using the pluto code to run 2D and 3D hydrodynamic simulations of protoplanetary discs with embedded 30 and 300 M⊕ planets on both an inclined (i = 2.86°) and non-inclined orbit, using an α-viscosity of 4 × 10−3. We produce synthetic scattered light images of these discs at H-band wavelengths using the radiative transfer code radmc3d. We find that while the surface density evolution in 2D and 3D simulations of inclined and non-inclined planets remain fairly similar, their observational appearance is remarkably different. Most of the features seen in the synthetic H-band images are connected to density variations of the disc at around 3.3 scale heights above and below the mid-plane, which emphasizes the need for 3D simulations. Planets on sustained orbital inclinations disrupt the disc’s upper atmosphere and produce radically different observable features and intensity profiles, including shadowing effects and intensity variation of the order of 10–20 times the surrounding background. The vertical optical depth to the disc mid-plane for H-band wavelengths is τ ≈ 20 in the disc gap created by the high-mass planet. We conclude that direct imaging of planets embedded in the disc remains difficult to observe, even for massive planets in the gap.

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Regimes of Dry Convection above Wildfires: Sensitivity to Fire Line Details

Journal of the Atmospheric Sciences ◽

10.1175/2009jas3226.1 ◽

2010 ◽

Vol 67 (3) ◽

pp. 611-632 ◽

Cited By ~ 1

Author(s):

Michael T. Kiefer ◽

Matthew D. Parker ◽

Joseph J. Charney

Keyword(s):

Line Shape ◽

3D Model ◽

Three Dimensional ◽

Vertical Wind Shear ◽

Heating Rates ◽

3D Simulations ◽

Complex Phenomena ◽

2D And 3D ◽

The Impact ◽

Dry Convection

Abstract Fire lines are complex phenomena with a broad range of scales of cross-line dimension, undulations, and along-line variation in heating rates. While some earlier studies have examined parcel processes in two-dimensional simulations, the complexity of fire lines in nature motivates a study in which the impact of three-dimensional fire line details on parcel processes is examined systematically. This numerical modeling study aims to understand how fundamental processes identified in 2D simulations operate in 3D simulations where the fire line is neither straight nor uniform in intensity. The first step is to perform simulations in a 3D model, with no fire line undulations or inhomogeneity. In general, convective modes simulated in the 2D model are reproduced in the 3D model. In one particular case with strong vertical wind shear, new convection develops separate from the main line of convection as a result of local changes to parcel speed and heating. However, in general the processes in the 2D and 3D simulations are identical. The second step is to examine 3D experiments wherein fire line shape and along-line inhomogeneity are varied. Parcel heating, as well as convective mode, is shown to exhibit sensitivity to fire line shape and along-line inhomogeneity.

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