Eulerian-Eulerian Modeling of Multiple Jet Interactions for Different Distributor Plates

2012 ◽  
Author(s):  
Santhip Krishnan Kanholy ◽  
Francine Battaglia
Keyword(s):  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Cfd Modeling ◽  
Particle Interactions ◽  
Two Dimensional ◽  
Jet Interactions ◽  
Eulerian Modeling ◽  
Distributor Plate

The hydrodynamics of fluidized beds involving gas and particle interactions are very complex, and must be carefully considered when modeling such a system using computational fluid dynamics (CFD). One of the issues involved is the interaction of multiple jets that develop above the distributor plate, which impacts the uniformity of fluidization. Using the common approach of a uniform gas velocity inlet boundary condition may not accurately represent distributor plates with nonuniform holes. The numerical approach will use a multi-fluid Eulerian-Eulerian CFD modeling to predict and examine the hydrodynamics of interacting jets. The present work will model a quasi-two-dimensional (2D) fluidized bed to compare with a corresponding experimental setup designed to examine multiple jet interactions for a distributor plate with 9 holes. Two-dimensional and three-dimensional simulations of the quasi-2D bed will be compared with experiments by investigating solid volume fraction distributions and solid flux distributions with agreeable results qualitatively. Use of experimental data in determining the amount of mass fluidizing will also be assessed using CFD. The efficacy of the new approach in capturing the hydrodynamics is demonstrated.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

Modeling Approaches to Accurately Predict Minimum Fluidization Characteristics of Gas-Solid Fluidized Beds

2012 ◽  
Author(s):  
Santhip Krishnan Kanholy ◽  
Francine Battaglia
Keyword(s):  
Binary Mixtures ◽  
Fluidized Beds ◽  
Solid Phase ◽  
Cfd Modeling ◽  
Particle Interactions ◽  
Dead Zones ◽  
Modeling Approaches ◽  
Minimum Fluidization ◽  
Computational Fluid Dynamics Cfd ◽  
Eulerian Modeling

The hydrodynamics of fluidized beds involving gas and particle interactions are very complex and must be carefully considered when using computational fluid dynamics (CFD). Modeling particle interactions are even more challenging for binary mixtures composed of varying particle characteristics such as diameter or density. One issue is the presence of dead-zones, regions of particles that do not fluidize and accumulate at the bottom, affecting uniform fluidization. In Eulerian-Eulerian modeling, the solid phase is assumed to behave like a fluid and the presence of dead zones are not typically captured in a simulation. Instead, the entire bed mass present in an experiment is modeled, which assumes full fluidization. The paper will present modeling approaches that account for only the fluidizing mass by adjusting the initial mass present in the bed using pressure drop and minimum fluidization velocity from experiments. In order to demonstrate the fidelity of the new modeling approach, different bed materials are examined. Binary mixture models are also validated for two types of mixtures consisting of glass-ceramic and ceramic-ceramic compositions. It will be shown that adjusting the mass in the modeling of fluidized beds best represents the measured quantities of an experiment for both single-phase and binary mixtures.

Dispersion of solids in fracturing flows of yield stress fluids

2017 ◽  
Vol 830 ◽  
pp. 93-137 ◽  
Author(s):  
S. Hormozi ◽  
I. A. Frigaard
Keyword(s):  
Yield Stress ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Process Variations ◽  
Model Framework ◽  
Shear Rates ◽  
Low Viscosity ◽  
High Shear Rates ◽  
Solids Concentration

Solids dispersion is an important part of hydraulic fracturing, both in helping to understand phenomena such as tip screen-out and spreading of the pad, and in new process variations such as cyclic pumping of proppant. Whereas many frac fluids have low viscosity, e.g. slickwater, others transport proppant through increased viscosity. In this context, one method for influencing both dispersion and solids-carrying capacity is to use a yield stress fluid as the frac fluid. We propose a model framework for this scenario and analyse one of the simplifications. A key effect of including a yield stress is to focus high shear rates near the fracture walls. In typical fracturing flows this results in a large variation in shear rates across the fracture. In using shear-thinning viscous frac fluids, flows may vary significantly on the particle scale, from Stokesian behaviour to inertial behaviour across the width of the fracture. Equally, according to the flow rates, Hele-Shaw style models give way at higher Reynolds number to those in which inertia must be considered. We develop a model framework able to include this range of flows, while still representing a significant simplification over fully three-dimensional computations. In relatively straight fractures and for fluids of moderate rheology, this simplifies into a one-dimensional model that predicts the solids concentration along a streamline within the fracture. We use this model to make estimates of the streamwise dispersion in various relevant scenarios. This model framework also predicts the transverse distributions of the solid volume fraction and velocity profiles as well as their evolutions along the flow part.

Truss Analyses by DQEM

1999 ◽  
Author(s):  
Chang-New Chen
Keyword(s):  
Algebraic Equation ◽  
Domain Boundary ◽  
Three Dimensional ◽  
Equation System ◽  
Numerical Approach ◽  
Differential Quadrature ◽  
Two Dimensional ◽  
Rigorous Solution ◽  
Differential Quadrature Element Method ◽  
Quadrature Element Method

Abstract A new numerical approach for solving generic three-dimensional truss problems having nonprismatic members is developed. This approach employs the differential quadrature (DQ) technique to discretize the element-based governing differential equations, the transition conditions at joints and the boundary conditions on the domain boundary. A global algebraic equation system can be obtained by assembling all of the discretized equations. A numerically rigorous solution can be obtained by solving the global algebraic equation system. Mathematical formulations for two-dimensional differential quadrature element method (DQEM) truss model are carried out. By using this DQEM model, accurate results of two-dimensional truss problems can efficiently be obtained. Numerical results demonstrate this DQEM model.

Fluid flow and heat transfer of a stratified system during natural convection – influence of chamfered corners

2019 ◽  
Vol 29 (2) ◽  
pp. 470-486 ◽  
Author(s):  
Alireza Rahimi ◽  
Aravindhan Surendar ◽  
Aygul Z. Ibatova ◽  
Abbas Kasaeipoor ◽  
Emad Hasani Malekshah
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Immiscible Fluids ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose This paper aims to investigate the three-dimensional natural convection and entropy generation in the rectangular cuboid cavities included by chamfered triangular partition made by polypropylene. Design/methodology/approach The enclosure is filled by multi-walled carbon nanotubes (MWCNTs)-H2O nanofluid and air as two immiscible fluids. The finite volume approach is used for computation. The fluid flow and heat transfer are considered with combination of local entropy generation due to fluid friction and heat transfer. Moreover, a numerical method is developed based on three-dimensional solution of Navier–Stokes equations. Findings Effects of side ratio of triangular partitions (SR = 0.5, 1 and 2), Rayleigh number (103 < Ra < 105) and solid volume fraction (f = 0.002, 0.004 and 0.01 Vol.%) of nanofluid are investigated on both natural convection characteristic and volumetric entropy generation. The results show that the partitions can be a suitable method to control fluid flow and energy consumption, and three-dimensional solutions renders more accurate results. Originality/value The originality of this work is to study the three-dimensional natural convection and entropy generation of a stratified system.

Numerical Simulation for Mechanical Behavior of Carbon Black Filler Particle Reinforced Rubber Matrix Composites

2011 ◽  
Vol 137 ◽  
pp. 1-6
Author(s):  
Qing Li ◽  
Xiao Xiang Yang
Keyword(s):  
Carbon Black ◽  
Mechanical Behavior ◽  
Plane Stress ◽  
Volume Fraction ◽  
Filler Particle ◽  
Three Dimensional ◽  
Rubber Matrix ◽  
Two Dimensional ◽  
Rubber Composites ◽  
Dimensional Plane

In this paper, the micromechanical finite element method based on Representative Volume Element has been applied to study and analyze the macro mechanical properties of the carbon black filled rubber composites by using two-dimensional plane stress simulations and three-dimensional axisymmetric simulations under uniaxial compression respectively. The dependence of the macroscopic stress-strain behavior and the effective elastic modulus of the composites, on particle shape, particle area/volume fraction and particle stiffness has been investigated and discussed. Additionally, the simulation results of the two-dimensional plane stress model and the three-dimensional axisymmetric model are evaluated and compared with the experimental data, which shows that the two-dimensional plane stress simulations generate poor predictions on the mechanical behavior of the carbon black particle reinforced rubber composites, while the three-dimensional axisymmetric simulations appear to give a better prediction.

scholarly journals Investigation of microvascular morphological measures for skeletal muscle tissue oxygenation by image-based modelling in three dimensions

2017 ◽  
Vol 14 (135) ◽  
pp. 20170635 ◽  
Author(s):  
B. Zeller-Plumhoff ◽  
K. R. Daly ◽  
G. F. Clough ◽  
P. Schneider ◽  
T. Roose
Keyword(s):  
Skeletal Muscle ◽  
Muscle Tissue ◽  
Cross Sections ◽  
Tissue Oxygenation ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Capillary Density ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Contrast Imaging

The supply of oxygen in sufficient quantity is vital for the correct functioning of all organs in the human body, especially for skeletal muscle during exercise. Traditionally, microvascular oxygen supply capability is assessed by the analysis of morphological measures on transverse cross-sections of muscle, e.g. capillary density or capillary-to-fibre ratio. In this work, we investigate the relationship between microvascular structure and muscle tissue oxygenation in mice. Phase contrast imaging was performed using synchrotron radiation computed tomography (SR CT) to visualize red blood cells (RBCs) within the microvasculature in mouse soleus muscle. Image-based mathematical modelling of the oxygen diffusion from the RBCs into the muscle tissue was subsequently performed, as well as a morphometric analysis of the microvasculature. The mean tissue oxygenation was then compared with the morphological measures of the microvasculature. RBC volume fraction and spacing (mean distance of any point in tissue to the closest RBC) emerged as the best predictors for muscle tissue oxygenation, followed by length density (summed RBC length over muscle volume). The two-dimensional measures of capillary density and capillary-to-fibre ratio ranked last. We, therefore, conclude that, in order to assess the states of health of muscle tissue, it is advisable to rely on three-dimensional morphological measures rather than on the traditional two-dimensional measures.

Three-Dimensional Printed Dielectric Substrates for Radio Frequency Applications

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Vana Snigdha Tummala ◽  
Ahsan Mian ◽  
Nowrin H. Chamok ◽  
Dhruva Poduval ◽  
Mohammod Ali ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Acrylonitrile Butadiene Styrene ◽  
Volume Fractions ◽  
The Core ◽  
Sandwich Construction ◽  
3D Printed ◽  
Rf Antenna

Engineered porous structures are being used in many applications including aerospace, electronics, biomedical, and others. The objective of this paper is to study the effect of three-dimensional (3D)-printed porous microstructure on the dielectric characteristics for radio frequency (RF) antenna applications. In this study, a sandwich construction made of a porous acrylonitrile butadiene styrene (ABS) thermoplastic core between two solid face sheets has been investigated. The porosity of the core structure has been varied by changing the fill densities or percent solid volume fractions in the 3D printer. Three separate sets of samples with dimensions of 50 mm × 50 mm × 5 mm are created at three different machine preset fill densities each using LulzBot and Stratasys dimension 3D printers. The printed samples are examined using a 3D X-ray microscope to understand pore distribution within the core region and uniformity of solid volumes. The nondestructively acquired 3D microscopy images are then postprocessed to measure actual solid volume fractions within the samples. This measurement is important specifically for dimension-printed samples as the printer cannot be set for any specific fill density. The experimentally measured solid volume fractions are found to be different from the factory preset values for samples prepared using LulzBot printer. It is also observed that the resonant frequency for samples created using both the printers decreases with an increase in solid volume fraction, which is intuitively correct. The results clearly demonstrate the ability to control the dielectric properties of 3D-printed structures based on prescribed fill density.

Rapid Three-Dimensional Segmentation of the Carotid Bifurcation From Serial MR Images

1999 ◽  
Vol 122 (1) ◽  
pp. 96-99 ◽  
Author(s):  
H. M. Ladak ◽  
J. S. Milner and ◽  
D. A. Steinman
Keyword(s):  
Ex Vivo ◽  
Current Trend ◽  
Three Dimensional ◽  
Carotid Bifurcation ◽  
Cfd Modeling ◽  
Black Blood ◽  
Two Dimensional ◽  
Surface Geometry ◽  
Three Dimensional Segmentation

The current trend in computational hemodynamics is to employ realistic models derived from ex vivo or in vivo imaging. Such studies typically produce a series of images from which the lumen boundaries must first be individually extracted (i.e., two-dimensional segmentation), and then serially reconstructed to produce the three-dimensional lumen surface geometry. In this paper, we present a rapid three-dimensional segmentation technique that combines these two steps, based on the idea of an expanding virtual balloon. This three-dimensional technique is demonstrated in application to finite element meshing and CFD modeling of flow in the carotid bifurcation of a normal volunteer imaged with black blood MRI. Wall shear stress patterns computed using a mesh generated with the three-dimensional technique agree well with those computed using a mesh generated from conventional two-dimensional segmentation and serial reconstruction. In addition to reducing the time required to extract the lumen surface from hours to minutes, our approach is easy to learn and use and requires minimal user intervention, which can potentially increase the accuracy and precision of quantitative and longitudinal studies of hemodynamics and vascular disease. [S0148-0731(00)00201-6]

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