scholarly journals APPLICATION OF THE LINEAR SPRING-DASHPOT MODEL IN THE CFD-DEM SIMULATION OF ALUMINA FLUIDIZATION

2015 ◽  
Vol 14 (2) ◽  
pp. 95
Author(s):  
A. M. C. Branco Jr ◽  
A. L. A. Mesquita ◽  
J. R. P. Vaz
Keyword(s):  
Experimental Data ◽  
Fluidized Beds ◽  
Limiting Factors ◽  
Uniform Size ◽  
Ansys Fluent ◽  
Dem Simulation ◽  
Linear Spring ◽  
Computational Fluid Dynamics Cfd ◽  
Drag Models ◽  
Particle Approach

The coupling of the Computational Fluid Dynamics (CFD) to the Discrete Element Method (DEM) to simulate fluidization is computationally demanding. Although the Linear Spring-Dahspot (LSD) model can help to reduce the CFD-DEM simulation runtime due to its simplicity, its applicability is not reasonable for all sorts of problems. The objective of the present work is to show the application of the LSD model to the CFD-DEM simulation of alumina fluidization. The simulations were carried out with the software ANSYS FLUENT 14.5 and divided into two parts: (1) the reproduction with ANSYS FLUENT of simulations from the literature in which the LSD model and a representative particle approach were used. (2) the simulation of alumina fluidization and validation with experimental data. The results of three main sets of parameters were analysed to include different DEM and CFD time steps, drag models, the representation of particles with both uniform size and particle size distribution, etc. The main conclusion of this work is that the LSD model and the CFD-DEM approach can be used to model the actual behaviour of alumina fluidized beds, but the high simulation runtime and the correct setting of the strategies used to control it are still limiting factors which deserve special attention.

A CFD Study of Existing Drag Models for Geldart A Particles in Bubbling Fluidized Beds

2014 ◽  
Author(s):  
Bahareh Estejab ◽  
Francine Battaglia
Keyword(s):  
Experimental Data ◽  
Fluidized Beds ◽  
Fine Particles ◽  
The Other ◽  
Particle Interactions ◽  
Model Group ◽  
Drag Model ◽  
Numerical Studies ◽  
Solid Phases ◽  
Drag Models

In this study, seven drag models are examined to determine how they affect fluidization behavior of Geldart A particles of biomass and coal. Notwithstanding the notable number of numerical studies to find the best drag model for larger particles, there is a dearth of information related to drag models for finer Geldart A particles. Additionally, to our knowledge, these drag models have not been tested with a binary mixture of Geldart A particles. Computational fluid dynamics was used to model the gas and solid phases in an Eulerian-Eulerain approach to simulate the particle-particle interactions of coal-biomass mixtures and compare the predictions with experimental data. In spite of the previous findings that bode badly for using predominately Geldart B drag models for fine particles, the results of our study reveal that if static regions of mass in the fluidized beds are considered, these drag models work well with Geldart A particles. It was found that the seven drag models could be divided into two categories based on their performance. One category included the Gidaspow family of drag models (Gidaspow, Gidaspow-Blend, and Wen-Yu) and the Syamlal-O’Brien drag model; these models closely predicted the experiments for single solids phase fluidization. For binary mixtures, however, the other drag model group (BVK, HYS, Koch and Hill) yielded better predictions.

Calibration of External Heat Transfer Coefficients During Cooling of a Partially-Filled Water Tank Using Measured Temperature-Time Data

2018 ◽  
Author(s):  
Vishal Ramesh ◽  
Sandip Mazumder ◽  
Gurpreet Matharu ◽  
Dhaval Vaishnav ◽  
Syed Ali ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Measured Temperature ◽  
Water Tank ◽  
Time Data ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients ◽  
Computational Fluid Dynamics Cfd ◽  
Temperature Time

A combined Computational Fluid Dynamics (CFD) and experimental approach is presented to determine (calibrate) the external convective heat transfer coefficients (h) around a partially-filled water tank cooled in a climactic chamber. A CFD analysis that includes natural convection in both phases (water and air) was performed using a 2D-axisymmetric tank model with three prescribed average heat transfer coefficients for the top, side and bottom walls of the tank. The commercial CFD code ANSYS-Fluent™, along with User-Defined Functions (UDFs), were utilized to compute and extract temperature vs. time curves at five different thermocouple locations within the tank. The prescribed h values were then altered to match experimentally obtained temperature-time data at the same locations. The calibration was deemed successful when results from the simulations exhibited match with experimental data within ±2°C for all thermocouples. The calibrated h values were finally used in full-scale 3D simulations and compared to the experimental data to test their accuracy. Predicted 3D results were found to agree with experimental results within the error of the calibration, thereby lending credibility to the overall approach.

CFD Simulation of Slug Dissipation in an Enlarged Impacting Tee

2019 ◽  
Author(s):  
Mobina Mohammadikharkeshi ◽  
Mazdak Parsi ◽  
Ramin Dabirian ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Experimental Data ◽  
Void Fraction ◽  
Cfd Simulation ◽  
Petroleum Industry ◽  
Production Operation ◽  
Cfd Simulations ◽  
Ansys Fluent ◽  
Transient Model ◽  
Diameter Pipe ◽  
Computational Fluid Dynamics Cfd

Abstract Slug flow, which commonly occurs in the petroleum industry, is not always a desired flow pattern due to production operation problems it may cause in pipelines and processing facilities. To mitigate these problems, flow conditioning devices such as multiphase flow manifolds and slug catchers are used, where dissipation of slugs occurs in downward flow or in larger diameter pipe sections. Tee-junctions are important parts of these flow conditioning devices. In this work, Computational Fluid Dynamics (CFD) simulations are conducted using ANSYS/FLUENT 17.2 to investigate slug dissipation in an Enlarged Impacting Tee-Junction (EIT). An Eulerian–Eulerian MultiFluid VOF transient model in conjunction with the standard k-ε turbulent model is used to simulate slug dissipation in an EIT geometry. The EIT consists of a 0.05 m ID 10 m long inlet, which is connected to the center of a 0.074 m ID 5.5 m long section that forms the EIT branches. Moreover, experimental data are acquired on slug dissipation lengths in a horizontal EIT with a similar geometry as in the CFD simulations. The CFD results include the mean void fraction and cross-sectionally averaged void fraction time series in the EIT for different gas and liquid velocities. These results provide the inlet slug length and dissipation length in the EIT branches. The CFD results are evaluated against the experimental data demonstrating that the slug dissipation occurring in EIT branches can be predicted by simulation.

scholarly journals Evaluation of different mathematical models in the CFD-DEM simulation of conical spouted bed fluid dynamics

2021 ◽  
pp. 2-2
Author(s):  
J.N Batista ◽  
R. Béttega
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Fluid Dynamic ◽  
Turbulence Models ◽  
Particle Rotation ◽  
Dem Simulation ◽  
Sorghum Grains ◽  
Drag Models ◽  
Semi Empirical ◽  
Best Fit

The input parameters, empirical, and semi-empirical models significantly influence the responses obtained by CFD-DEM simulations. In this work, the effect of three turbulence models, three conditions of the particle rotation, and five drag models on the fluid dynamic behavior of a conical spout bed applied to the drying of sorghum grains were evaluated. Experimental data on the solids pressure drop, height, and shape of the fountain were used to validate the simulations. Results showed the importance of including the particle rotation in the model to approximate the results simulated with the experimental behavior. Compared with experimental data, considering the particle rotation by Dennis et al. model, the deviation was of the 2% for the fountain height and 9.18% for the pressure drop. While for the model without the particle rotation, the deviations were 106.33% and 42.31% for the fountain height and pressure drop, respectively. For the analyzed case, the standard k-? turbulence model showed a greater agreement with the experimental data. For the drag models evaluated, the best fit with the experimental data was obtained by the Koch-Hill drag model, followed by the Gidaspow model, with deviations less than 10%.

scholarly journals Effect of Bench Hood Exhaust Usage on Indoor Air Quality in a Chemical Laboratory

2014 ◽  
Vol 1 ◽  
pp. 14-22
Author(s):  
Ayman A. Shaaban ◽  
Samy M. Morcos ◽  
Essam Eldin Khalil ◽  
Mahmoud A. Fouad
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Mole Fraction ◽  
Indoor Air ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Computational Fluid Dynamics Cfd

Indoor air quality inside chemical laboratories subjected to gaseous contaminants was investigated numerically throughout the current research using Ansys Fluent 13. The lab is 4.8 m (L) * 4.3 m (W) * 2.73 m (H). The model was built and mesh was generated using Gambit 2.2.30 yielding around 1.4 million cells. To ensure the reliability of the Computational Fluid Dynamics (CFD) model validation was done against experimental data of three cases done by Jin et al. [1]. The model could simulate accurately contaminant mole fraction to the order of 10 Indoor air quality inside chemical laboratories subjected to gaseous contaminants was investigated numerically throughout the current research using Ansys Fluent 13. The lab is 4.8 m (L) * 4.3 m (W) * 2.73 m (H). The model was built and mesh was generated using Gambit 2.2.30 yielding around 1.4 million cells. To ensure the reliability of the Computational Fluid Dynamics (CFD) model validation was done against experimental data of three cases done by Jin et al. [1]. The model could simulate accurately contaminant mole fraction to the order of 10.

CFD Simulation of Round Impinging Jet and Comparison With Experimental Data

2016 ◽  
Author(s):  
H. Arabnejad ◽  
A. Mansouri ◽  
S. A. Shirazi ◽  
B. S. McLaury
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Cfd Simulation ◽  
Turbulence Models ◽  
Impinging Jet ◽  
Reynolds Stress Model ◽  
Ansys Fluent ◽  
Target Wall ◽  
Computational Fluid Dynamics Cfd ◽  
Better Than

In this work, fluid dynamics of a turbulent round impinging jet has been studied using Computational Fluid Dynamics (CFD) and the results have been compared with experimental data from the literature. The fluid was water with density of 1000 kg/m3 and the average velocity of the submerged jet was kept constant at 10.7 m/s while the liquid viscosity varied from 1 cP to 100 cP. Different turbulence models including k-ε, k-ω and Reynolds Stress Model (RSM) have been employed in ANSYS FLUENT and the predicted axial and radial velocity profiles at various distances from the wall are compared with LDV data. It was observed that at locations away from the target wall, predicted velocities are comparable to the measured velocities for all the viscosities. However, near the wall, the deviation between the CFD predictions and experimental measurements become noticeable. The performance of k-ω model and RSM are found to be better than the k-ε model especially for the highest viscous fluid, but no model was found to be superior for all conditions and at all locations.

scholarly journals Some Tips on Numerical Modeling of Airflow and Fires in Road Tunnels

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2366
Author(s):  
Aleksander Król ◽  
Małgorzata Król
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Ventilation System ◽  
Fire Dynamics ◽  
Safety Level ◽  
Ansys Fluent ◽  
Software Packages ◽  
Road Tunnels ◽  
Computational Fluid Dynamics Cfd ◽  
Emergency Mode

The efficiency of tunnels systems is often evaluated using numerical simulations. This concerns both to normal and emergency mode of tunnel systems operation. Therefore the safety level of tunnel users may depend on the quality of numerical models being built. The most often studied areas cover the researches on natural and forced airflows in the normal mode and on fire development and smoke spreading in the emergency mode as well as modeling of fan operation. Thus, many software packages implementing Computational Fluid Dynamics (CFD) are applied here. Despite the available software is recognized as reliable, the problem arises because the built numerical models should be validated at least partially with experimental data. There is a shortage of experimental data from real tunnels due to high costs and many organizational or formal difficulties. Some researchers use data from scaled experiments, but this leads to problems connected with scaling. The paper presents the application of two widely used software packages—Fire Dynamics Simulator (FDS) and ANSYS Fluent to reproduce some scenarios of the operation of a tunnel ventilation system for normal and emergency mode. Most of results were compared with data obtained by own full scale measurements or data available in literature. Some practical issues concerning the application of FDS and ANSYS Fluent were discussed as well.

Effects of Over Fire Air on the Combustion and NOx Emission Characteristics of a 600 MW Opposed Swirling Fired Boiler

2012 ◽  
Vol 512-515 ◽  
pp. 2135-2142 ◽  
Author(s):  
Yu Peng Wu ◽  
Zhi Yong Wen ◽  
Yue Liang Shen ◽  
Qing Yan Fang ◽  
Cheng Zhang ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Empirical Method ◽  
Nox Emission ◽  
Emission Characteristics ◽  
Cfd Model ◽  
Nitrogen Release ◽  
Computational Fluid Dynamics Cfd ◽  
Low Nox Emission

A computational fluid dynamics (CFD) model of a 600 MW opposed swirling coal-fired utility boiler has been established. The chemical percolation devolatilization (CPD) model, instead of an empirical method, has been adapted to predict the nitrogen release during the devolatilization. The current CFD model has been validated by comparing the simulated results with the experimental data obtained from the boiler for case study. The validated CFD model is then applied to study the effects of ratio of over fire air (OFA) on the combustion and nitrogen oxides (NOx) emission characteristics. It is found that, with increasing the ratio of OFA, the carbon content in fly ash increases linearly, and the NOx emission reduces largely. The OFA ratio of 30% is optimal for both high burnout of pulverized coal and low NOx emission. The present study provides helpful information for understanding and optimizing the combustion of the studied boiler

scholarly journals Experimental and CFD Simulations of the Aerosol Flow in the Air Ventilating the Underground Excavation in Terms of SARS-CoV-2 Transmission

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4743
Author(s):  
Tomasz Janoszek ◽  
Zbigniew Lubosik ◽  
Lucjan Świerczek ◽  
Andrzej Walentek ◽  
Jerzy Jaroszewicz
Keyword(s):  
Numerical Calculations ◽  
Mining Institute ◽  
Ventilation Network ◽  
Underground Excavation ◽  
In Situ Tests ◽  
Ansys Fluent ◽  
Aerosol Emission ◽  
Ansys Cfx ◽  
Computational Fluid Dynamics Cfd

The paper presents the results of experimental and model tests of transport of dispersed fluid droplets forming a cloud of aerosol in a stream of air ventilating a selected section of the underground excavation. The excavation selected for testing is part of the ventilation network of the Experimental Mine Barbara of the Central Mining Institute. For given environmental conditions, such as temperature, pressure, relative humidity, and velocity of air, the distribution of aerosol droplet changes in the mixture of air and water vapor along the excavation at a distance was measured at 10 m, 25 m, and 50 m from the source of its emission. The source of aerosol emission in the excavation space was a water nozzle that was located 25 m from the inlet (inlet) of the excavation. The obtained results of in situ tests were related to the results of numerical calculations using computational fluid dynamics (CFD). Numerical calculations were performed using Ansys-Fluent and Ansys-CFX software. The dimensions and geometry of the excavation under investigation are presented. The authors describe the adopted assumptions and conditions for the numerical model and discuss the results of the numerical solution.

scholarly journals CFD-DEM Simulation of Spouted Bed Dynamics under High Temperature with an Adhesive Model

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2276
Author(s):  
Zhao Chen ◽  
Lin Jiang ◽  
Mofan Qiu ◽  
Meng Chen ◽  
Rongzheng Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Particle Surface ◽  
Particle Collision ◽  
Gas Velocity ◽  
Spouted Bed ◽  
Dem Simulation ◽  
Linear Spring ◽  
Adhesion Model ◽  
Adhesive Model ◽  
Damping Model

Particle adhesion is of great importance to coating processes due to its effect on fluidization. Currently, Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) has become a powerful tool for the study of multiphase flows. Various contact force models have also been proposed. However, particle dynamics in high temperature will be changed with particle surface properties changing. In view of this, an adhesion model is developed based on approaching-loading-unloading-detaching idea and particle surface change under high temperature in this paper. Analyses of the adhesion model are given through two particle collision process and validated by experiment. Effects of inlet gas velocity and adhesion intensity on spouted bed dynamics are investigated. It is concluded that fluidization cycle will be accelerated by adhesion, and intensity of fluidization will be marginally enhanced by slight adhesion. Within a certain range, increasing inlet gas velocity will lead to strong intensity of particle motion. A parameter sensitivity comparison of linear spring-damping model and Hertz-Mindlin Model is given, which shows in case of small overlaps, forces calculated by both models have little distinction, diametrically opposed to that of large overlaps.

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