Engineering Commons^™

Effect Of Particle Size Distribution On The Performance Of A Catalytic Fluidized Bed Reactor, Sanjib Das Sharma, Todd S. Pugsley

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Computational Fluid Dynamics (CFD) has been used to model ozone decomposition in a two-dimensional fluidized bed of 2.0 meters height and 0.1 m width. Simulations were carried out with mono-size, bimodal, and wide catalyst particle size distributions with the same mean diameter to model the effect of fines on the reaction. CFD predictions fall within 20% of the experimental data.

A Cfd Study Into The Influence Of The Particle Particle Drag Force On The Dynamics Of Binary Gas Solid Fluidized Beds, Olumuyiwa Owoyemi, Paola Lettieri

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

This paper presents a preliminary CFD study into the effect of the particle-particle interphase mo- mentum transfer term on the mixing and bubble dynamics of a binary gas solid fluidized consisting of particles which only differ in size. A new fluid dynamic model, implemented within a commercial CFD code, CFX4.4, is used to model the binary mixture. The governing fluid dynamic relationships for the solid phases and the fluid phase are based on “the elastic force” concept from the Particle Bed Model (1, 2). The solids pressure for each of the particulate phases is not taken into consideration in this …

Dynamic Response Characteristics Of Local Capacitive Measurement Devices With Application To Cfd Validation, Clay R. Sutton, John Chen

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The Two-Fluid Model (TFM) approach to modeling fluid-solid systems holds great promise as a means to simulate arbitrary systems, thus greatly reducing design and scale-up efforts. Unfortunately, comprehensive experimental validations of these models are still in short supply. This work addresses this issue by proposing a framework under which to relate computational fluid dynamics model results with experimental measurements on a one-to-one basis. Specifically this is performed for the case of local solids concentration transients in a bench-scale bubbling fluidized bed. The manner in which this comparison is performed has implications for the conclusions that may be drawn for a …

Homogeneous To Bubbling Regime Transition In Gas- And Liquid-Fluidized Beds Through Dem-Cfd Simulations, Alberto Di Renzo, Francesco P. Di Maio

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

DEM-CFD simulations are carried out for the water fluidization of 200 micron glass ballotini and air fluidization of cohesionless alumina 70 micron powders. In the first case, homogeneous expansion is found throughout the whole investigated range of water velocity. Alumina powders exhibits a transition to bubbling regime at a voidage value in very good agreement with results of the theory of particle bed stability. The simulated kinematic and dynamic wave propagation velocities are in good agreement with theoretical predictions.

A New Fluid Dynamic Model For The Cfd Simulations Of Fluidized Beds, Luca Mazzei, Paola Lettieri

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

A new Eulerian-Eulerian multidimensional model is proposed for the study of the dynamics of dense fluidized suspensions. The main distinctive feature of this new formulation of the equations of motion resides in the closure relationships adopted to express the fluid-particle interaction force. The force accounts for three contributions: buoyant force, drag force and elastic force. The buoyant force is related to the weight of the fluid displaced by the particles. The drag force is expressed as the product of the drag exerted on an unhindered particle, subject to the same volumetric flux of fluid, and a “corrective function” dependent on …

An Investigation Of Fluidized Bed Scaling Laws By Dem Simulation, John Sanderson, Martin J Rhodes, X. Shan Wang, K. Seng Lim

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

A preliminary investigation of the scaling laws for bubbling fluidized beds was undertaken using Discrete Element Method simulation. Six 2D and two 3D fluidized beds were simulated and compared using bed snapshots and dynamic pressure drop. Beds properly matched by the simplified criteria were in relatively poor agreement; agreement deteriorated further for a large scale change or a particle density mis-match. Simulations matched by the full scaling criteria agreed well at low velocities but deteriorated at higher velocities. The possible reasons for these results are discussed.

Numerical Study Of The Intrinsic And Feedback Dynamics Of A Gas-Solid Fluidized Bed, F. Bonniol, C. Sierra, R. Occelli, H. Bournot, L. Tadrist

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The aim of this paper is to understand the complex spatio-temporal patterning of the dense bed when the inlet conditions can be modified by the bed itself. In this study, the inlet conditions (fluid pressure and velocity upstream the bed) take into account resistive effects from the distributor and capacitive ones from the air-supply system (plenum). The present work addresses particularly the issue of the transition between multiple and single bubble regimes that occurs for some particular inlet conditions.

Comparison Of Simulated And Measured Flow Patterns: Solid And Gas Mixing In A 2d Turbulent Fluidized Bed, Ulla Ojaniemi, Sirpa Kallio, Alf Hermanson, Mikko Manninen, Maiju Seppälä, Veikko Taivassalo

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Results from experiments done in a 2D turbulent fluidized bed cold model are presented. Experiments were conducted to study flow patterns, particle mixing in the bed and spreading of gas blown from one side into the bed. 2D simulations of the experiments were carried out using the Eulerian multiphase models of the Fluent and MFIX CFD softwares.

Prediction Of The Dynamics Of A Fluidized Bed Reactor Using Artificial Neural Networks, Shayan Karimipour, Navid Mostoufi, Rahmat Sotudeh -Gharebagh

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The dynamic behavior of fluidized bed has been studied based on the chaos theory. The experiments were done in a fluidized bed of 0.15 m diameter using an optical fiber probe. The interval between successive clusters in the fluidized bed were calculated from the time series signals and proved to be chaotic by calculating the correlation dimension. An artificial neural network (ANN) was adapted and trained to predict the generated time series. The ANN results were compared with the predictions of the k-Nearest Neighbor (kNN) method to show the superiority of ANN in chaotic time series prediction.

Gas Fluidization And Pneumatic Conveying In Confined Beds: A Numerical Study, Yurong He, Thang Ngoc Cong, Yulong Ding, Huilin Lu

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The fluidization phenomena for gas-fine particle two-phase flow is numerically simulated in confined fluidized bed based on two-fluid model, applying body-fitted coordination for the irregular geometry zone in this work. The simulation was performed either with a partially packed fluidized bed in the bottom part applying various superficial gas velocities in bubbling region, which is used to study the bubbles formation and the average porosity in the packed zone, or with a whole packed fluidized bed applying various solid flux rates in pneumatic region, which is used to investigate the mechanism in the packed bed. The void fraction of the …

Discrete Particle Simulation Of The Gas-Solid Flow In A Circulating Fluidized Bed, K. W. Chu, B. Wang, Aibing Yu

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

This paper presents a numerical study of the gas-solid flow in a three-dimensional Circulating Fluidized Bed (CFB) by means of Combined Continuum and Discrete Method (CCDM) in which the motion of discrete particles is described by Discrete Particle Method (DPM) on the basis of Newton’s laws of motion applied to individual particles and the flow of continuum fluid by the traditional Computational Fluid Dynamics (CFD) based on the local averaged Navier-Stokes equations. The simulation is achieved by incorporating DPM codes into the commercial CFD software package Fluent. It is shown that the discrete particle simulation can capture the key flow …

Simulation Of A Pulsating Bed Using Eulerian Approach, Shyam Shankar Dokka, Hamid Arastoopour

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

A numerical study of the effect of gas pulsation on the flow pattern of solid particles in a two-dimensional gas-solid fluidized bed was conducted using the Eulerian granular kinetic theory. Our simulated bed dynamics agreed well with the experimental work of Koksal and Vural, and with the Discrete Element Method (DEM) model simulations of Tsuji et al.

A Discrete Particle Simulation Study Of Solids Mixing In A Pressurized Fluidized Bed, Willem Godlieb, Niels G. Deen, J.A.M. Kuipers

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

A fluidized bed containing polymeric particles is investigated using a state-of-the-art soft-sphere discrete particle model (DPM). The pressure dependency of particle mixing, flow patterns and bubble behaviour are analysed. It is found that with increasing pressure a less distinct bubble-emulsion structure and improved solids mixing can be observed.

Influence Of Bubble-Bubble Interactions On The Macroscale Circulation Patterns In A Bubbling Gas-Solid Fluidized Bed, J. A. Laverman, M. Van Sint Annaland, J.A.M. Kuipers

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The macro-scale circulation patterns in the emulsion phase of a gas-solid fluidized bed in the bubbling regime have been studied with a 3D Discrete Bubble Model. It has been shown that bubble-bubble interactions strongly influence the extent of the solids circulation and the bubble size distribution.

A Dem Study Of Geldart Group A Particle Bed Fluidisation Behavior Across The Regimes, Fang Yang, David K. Kafui, C. Thornton, J.P.K. Seville

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The objective of the study is to identify the transitions in bed behavior as the gas velocity is increased to cover the complete range from minimum fluidization through bubbling and turbulent behavior to pneumatic transport. The simulation data is examined in terms of computer visualizations, the rate of change of average bed voidage and pressure drop fluctuations.

Using Computational Fluid Dynamics Modeling To Improve The Performance Of A Solar Co2 Converter, Thomas H. Fletcher, Ralph J. Price, Reed J. Jensen

Faculty Publications

A solar collector to convert CO2 to CO at high temperature was previously developed, achieving a product with 4-6 mol % CO from pure CO2. Modeling results showed that reactions occurred in the thermal boundary layer of the heated zirconia rod at temperatures greater than 2300 K. This paper describes results of computer modeling of advanced designs meant to increase the conversion of CO from CO2. Several design modifications were tested using the model, including changing the cool-down region configuration, increasing the zirconia rod diameter, and changing the zirconia rod shape. Several operational adjustments were also modeled, including reducing the …

Critical Hypersonic Aerothermodynamic Phenomena, John J. Bertin, Russell M. Cummings

Aerospace Engineering

The challenges in understanding hypersonic flight are discussed and critical hypersonic aerothermodynamics issues are reviewed. The ability of current analytical methods, numerical methods, ground testing capabilities, and flight testing approaches to predict hypersonic flow are evaluated. The areas where aerothermodynamic shortcomings restrict our ability to design and analyze hypersonic vehicles are discussed, and prospects for future capabilities are reviewed. Considerable work still needs to be done before our understanding of hypersonic flow will allow for the accurate prediction of vehicle flight characteristics throughout the flight envelope from launch to orbital insertion.

Axial Stent Strut Angle Influences Wall Shear Stress After Stent Implantation: Analysis Using 3d Computational Fluid Dynamics Models Of Stent Foreshortening, John F. Ladisa, Lars E. Olson, Douglas Anthony Hettrick, David C. Warltier, Judy R. Kersten, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Introduction

The success of vascular stents in the restoration of blood flow is limited by restenosis. Recent data generated from computational fluid dynamics (CFD) models suggest that the vascular geometry created by an implanted stent causes local alterations in wall shear stress (WSS) that are associated with neointimal hyperplasia (NH). Foreshortening is a potential limitation of stent design that may affect stent performance and the rate of restenosis. The angle created between axially aligned stent struts and the principal direction of blood flow varies with the degree to which the stent foreshortens after implantation.

Methods

In the current investigation, we …

Incorporating Computational Fluid Dynamics Into The Preliminary Design Cycle, Jonathan Knighton Shelley

Theses and Dissertations

Industry is constantly looking for ways to bring new or derivative products to market in the shortest amount of time for the least amount of money. To accomplish this, Industry has adopted Computer Aided Engineering (CAX) tools that perform structural, flow, manufacturing, and cost analysis. The way in which a company utilizes these CAX tools can determine the success of these new products. One of these tools that Industry often struggles with in the preliminary design of a product is Computational Fluid Dynamics (CFD). Some of the challenges presented by CFD are the time it takes to create a CAD …

Flow Pattern Visualization In A Mimic Anaerobic Digester Using Cfd, Mehul S. Vesvikar, Muthanna H. Al-Dahhan

Chemical and Biochemical Engineering Faculty Research & Creative Works

Three-Dimensional Steady-State Computational Fluid Dynamics (CFD) Simulations Were Performed in Mimic Anaerobic Digesters to Visualize their Flow Pattern and Obtain Hydrodynamic Parameters. the Mixing in the Digester Was Provided by Sparging Gas at Three Different Flow Rates. the Gas Phase Was Simulated with Air and the Liquid Phase with Water. the CFD Results Were First Evaluated using Experimental Data Obtained by Computer Automated Radioactive Particle Tracking (CARPT). the Simulation Results in Terms of overall Flow Pattern, Location of Circulation Cells and Stagnant Regions, Trends of Liquid Velocity Profiles, and Volume of Dead Zones Agree Reasonably Well with the Experimental Data. …

A Cad-Centric Approach To Cfd Analysis With Discrete Features, Matthew Lee King

Theses and Dissertations

During the conceptual design stage several concepts are generated, and a few are selected for detailed analyses. CAD models from conceptual design often follow the "over-the-wall" approach for downstream analyses such as FEA, CFD, heat transfer, and vibrations. A CAD-centric approach will be applied to the CAD-to-CFD process to help industry in an ongoing quest to shorten the design cycle time. The CAD-centric approach consists of using the CAD model as a source of data for downstream applications such as mesh generation, and CFD setup. The CAD model used in the CAD-centric approach contains the geometry to be analyzed and …

Effect Of Coriolis And Centrifugal Forces On Turbulence And Transport At High Rotation And Buoyancy Numbers, Ahmad Khalaf Sleiti

Electronic Theses and Dissertations

This study attempts to understand one of the most fundamental and challenging problems in fluid flow and heat transfer for rotating machines. The study focuses on gas turbines and electric generators for high temperature and high energy density applications, respectively, both which employ rotating cooling channels so that materials do not fail under high temperature and high stress environment. Prediction of fluid flow and heat transfer inside internal cooling channels that rotate at high rotation number and high density ratio similar to those that are existing in turbine blades and generator rotors is the main focus of this study. Both …

Large Eddy Simulation Based Turbulent Flow-Induced Vibration Of Fully Developed Pipe Flow, Matthew Thurlow Pittard

Theses and Dissertations

Flow-induced vibration caused by fully developed pipe flow has been recognized, but not fully investigated under turbulent conditions. This thesis focuses on the development of a numerical Fluid-Structure Interaction (FSI) model that will help define the relationship between pipe wall vibration and the physical characteristics of turbulent flow. Commercial FSI software packages are based on Reynolds Averaged Navier-Stokes (RANS) fluid models, which do not compute the instantaneous fluctuations in turbulent flow. This thesis presents an FSI approach based on Large Eddy Simulation (LES) flow models, which do compute the instantaneous fluctuations in turbulent flow. The results based on the LES …

Solution Of The Navier-Stokes Equations For Transonic Propeller Flows, Fergal Boyle

Conference Papers

The three-dimensional, compressible, viscous flow field around a general propeller geometry with the inflow at zero angles of incidence and yaw is computed using a Reynolds-Averaged Navier-Stokes equations solver. Results from validation test cases in which the laminar and turbulent incompressible flow over a flat plate are calculated demonstrate the flow solver is capable of accurately capturing boundary-layer behaviour. Euler solutions from flow field calculations around two very different propeller geometries show a high level of accuracy and efficiency. Preliminary results from a viscous flow field calculation around a two-bladed propeller are very encouraging.

An Efficient Procedure For Viscous Propeller Flow Field Calculations, Fergal Boyle

Conference Papers

An efficient procedure has been developed for the computation of the three-dimensional, compressible, viscous flow field around a general propeller geometry with the inflow at zero angles of incidence and yaw. The solution procedure combines a recently developed Reynolds-Averaged-Navier-Stokes equations solver with a commercially available grid generator designed specifically for turbomachinery configurations. Preliminary results from the calculation of laminar and turbulent incompressible flow over a flat plate demonstrate that the flow solver is capable of capturing boundary-layer behaviour accurately. Results from the prediction of the transonic flow over a two-bladed propeller geometry show that the procedure is accurate and efficient …

Comparative Analysis Of Rng K-E And 'Standard' K-C Models For Fluid Flow Around A Cylinder, A Temu

Tanzania Journal of Engineering and Technology (TJET)

A two-dimensional computational scheme for simulating fluid flow around a cylinder was investigated. RNG (Re-NOrmalisation Group) and 'standard' turbulent closure models were used. simulation was implemented with assistance OfFLOW-3D computational fluid dynamics (CFD) code. The governing equation Of fluid motion, in Eulerian form, included body forces as well as surface forces. The computational model predictions for fluid velocity showed good agreement between the two models. Comparison Of the viscosities showed a large deviation from the two models, with RNG k-E model giving a better approximation. Comparison Of the velocity around the cylinder, as obtained from RNG k-c model, with approximation …

Statistical Characterization Of Macroscale Multiphase Flow Textures In Trickle Beds, Y. Jiang, M. (Muthanna) H. Al-Dahhan, M. P. Duduković

Chemical and Biochemical Engineering Faculty Research & Creative Works

Experimental Studies (Lutran Et Al., Ind. Engng Chem. Res. 30 (1991) 1270; Ravindra Et Al., Ind. Engng Chem. Res. 36 (1997) 5133) and Numerical Simulation (Jiang Et Al., Chem. Engng Sci. 54 (1999) 2409-2419) Lead to the Conclusion that Fluid Flow Distribution in Trickle Beds is a Function of Bed Structure (I.e. Porosity Distribution), Particle External Wetting and Inlet Superficial Velocities of the Two Fluids. in This Study, Quantitative Relationships among the above Parameters Are Developed in a Statistical Manner through a Series of Computational Fluid Dynamics Simulations. the Contribution of Capillary Forces to Liquid Maldistribution is Significant in the …

Two-Phase Flow Distribution In 2d Trickle-Bed Reactors, Y. Jiang, M. R. Khadilkar, M. (Muthanna) H. Al-Dahhan, M. P. Dudukovic

Chemical and Biochemical Engineering Faculty Research & Creative Works

An Extended Discrete Cell Model (DCM), based on Minimization of Energy Dissipation Rate, is Applied to Predict Two-Phase Flow Distribution in the Two-Dimensional Trickle-Bed Reactors. the Main Advantages of DCM Are that It Can Qualitatively Capture the Experimental Observations, and Readily Distinguish between Flow Distribution in Prewetted and Non-Prewetted Beds, as Well as Reflect the Effects of Bed Structure and Inlet Liquid Distributor on Two Phase Flow Distribution. for Comparison Purpose, the Results of Liquid Distribution Obtained by DCM Are Compared with Both Computational Fluid Dynamics (CFD) Simulations and Experimental Observations in a 2D Bed. the Achieved Qualitative and Quantitative …