Erosion Evaluations of a Slurry Mixer Tank With Computational Fluid Dynamics Methods

2006 ◽  
Author(s):  
Si Y. Lee ◽  
Richard A. Dimenna ◽  
Glenn A. Taylor
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Leading Edge ◽  
Working Fluid ◽  
Shear Stresses ◽  
Internal Structures ◽  
Wall Shear ◽  
Erosion Loss ◽  
Solids Content ◽  
Cfd Analyses

This paper discusses the use of computational fluid dynamics (CFD) methods to understand and characterize erosion of the floor and internal structures in the slurry mixing vessels in the Defense Waste Processing Facility. An initial literature survey helped identify the principal drivers of erosion for a solids laden fluid: the solids content of the working fluid, the regions of recirculation and particle impact with the walls, and the regions of high wall shear. A series of CFD analyses was performed to characterize slurry-flow profiles, wall shear, and particle impingement distributions in key components such as coil restraints and the vessel floor. The calculations showed that the primary locations of high erosion resulting from abrasion were at the leading edge of the coil guide, the tank floor below the insert plate of the coil guide support, and the upstream lead-in plate. These modeling results based on the calculated high shear regions were in excellent agreement with the observed erosion sites in both location and the degree of erosion. Loss of the leading edge of the coil guide due to the erosion damage during the slurry mixing operation did not affect the erosion patterns on the tank floor. Calculations for a lower impeller speed showed similar erosion patterns but significantly reduced wall shear stresses.

scholarly journals Heat Transfer Enhancement and Flow Physics Behavior of Fluid in Circular Tube with Insert

2019 ◽  
Vol 8 (3) ◽  
pp. 1708-1715
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Behavior ◽  
Vortex Generator ◽  
Leading Edge ◽  
Working Fluid ◽  
Literature Study

The paper presents computational fluid dynamics study of non-conventional insert vortex generator using Commercial software, to analyze the effect of vortex generator insert on heat transfer augmentation and fluid flow behavior. The study was done for Reynolds number 10000, 15000, 25000, 35000 and 45000 with working fluid as air flowing through a tube with a constant heat flux of 1000 w/m2. Current study validates the experimental results from the literature study. The heat transfer of these inserts with various geometrical arrangements viz. pitch to projected length ratio, angle of attack and height to inner diameter ratio are investigated here with the help of computational fluid dynamics software. The physical mechanism of formation and development of vortex flow from the leading edge to trailing edge of the insert is studied and it is observed that Nusselt number increases as an increment in Reynolds number. The ratio of augmented Nusselt number to smooth tube Nusselt number is found to be decreasing with increase in Reynolds number.

Mesh Sensitivity Analysis for Quantitative Shear Stress Assessment in Blood Pumps Using Computational Fluid Dynamics

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Sascha Gross-Hardt ◽  
Fiete Boehning ◽  
Ulrich Steinseifer ◽  
Thomas Schmitz-Rode ◽  
Tim A. S. Kaufmann
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Transport Model ◽  
Leading Edge ◽  
Characteristic Number ◽  
Tip Clearance ◽  
Shear Stresses ◽  
Centrifugal Blood Pump ◽  
Blood Damage

The reduction of excessive, nonphysiologic shear stresses leading to blood trauma can be the key to overcome many of the associated complications in blood recirculating devices. In that regard, computational fluid dynamics (CFD) are gaining in importance for the hydraulic and hemocompatibility assessment. Still, direct hemolysis assessments with CFD remain inaccurate and limited to qualitative comparisons rather than quantitative predictions. An underestimated quantity for improved blood damage prediction accuracy is the influence of near-wall mesh resolution on shear stress quantification in regions of complex flows. This study investigated the necessary mesh refinement to quantify shear stress for two selected, meshing sensitive hotspots within a rotary centrifugal blood pump (the blade leading edge and tip clearance gap). The shear stress in these regions is elevated due to presence of stagnation points and the flow around a sharp edge. The nondimensional mesh characteristic number y+, which is known in the context of turbulence modeling, underestimated the maximum wall shear stress by 60% on average with the recommended value of 1, but was found to be exact below 0.1. To evaluate the meshing related error on the numerical hemolysis prediction, three-dimensional simulations of a generic centrifugal pump were performed with mesh sizes from 3 × 106 to 30 × 106 elements. The respective hemolysis was calculated using an Eulerian scalar transport model. Mesh insensitivity was found below a maximum y+ of 0.2 necessitating 18 × 106 mesh elements. A meshing related error of up to 25% was found for the coarser meshes. Further investigations need to address: (1) the transferability to other geometries and (2) potential adaptions on blood damage estimation models to allow better quantitative predictions.

scholarly journals Designing a Scaled Erosion Test With Computational Fluid Dynamics Methods

2002 ◽  
Author(s):  
S. Y. Lee ◽  
R. A. Dimenna ◽  
M. R. Duignan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Radioactive Waste ◽  
Liquid Radioactive Waste ◽  
Cross Flow ◽  
Full Scale ◽  
Test Facility ◽  
Working Fluid ◽  
Savannah River ◽  
Wall Shear

The Department of Energy is sponsoring the River Protection Project, which includes the design of a facility to stabilize liquid radioactive waste that is stored at the Hanford Site. Because of its experience with radioactive waste stabilization, the Savannah River Technology Center of the Westinghouse Savannah River Company is assisting in the development and testing of parts of the waste treatment process. One part of the process is the separation of highly radioactive solids from the liquid wastes by cross-flow ultrafiltration. For the projected forty-year life of the filtration facility, wear will occur from a combination of erosion and corrosion due to the flow of slurries. A scaled cross-flow filter facility will be tested with simulated waste to quantify the wear rate so that an effective maintenance schedule can be developed. This paper discusses the application of computational fluid dynamics (CFD) methods to ensure that the test facility design would capture the erosion phenomena expected in the full-scale cross-flow ultrafiltration facility. An initial literature survey helped identify the principal drivers of erosion for a solids laden fluid. These were the solids content of the working fluid, the regions of recirculation and particle impact with the walls, and the regions of high wall shear. A series of CFD analyses was then designed to characterize slurry-flow profiles, wall shear, and particle impingement distributions in key pipe bends and fittings representative of the plant. Pipe diameters, lengths, the locations of pipefittings, and slurry velocities were scaled with the CFD calculations to ensure that the erosion drivers were appropriately represented in the test facility. This resulted in a validation of the theoretical determination of those drivers, and allowed the test results to be applied to a prediction of wear in the full-scale filtration facility.

scholarly journals Fluid mechanics of human fetal right ventricles from image-based computational fluid dynamics using 4D clinical ultrasound scans

2016 ◽  
Vol 311 (6) ◽  
pp. H1498-H1508 ◽  
Author(s):  
Hadi Wiputra ◽  
Chang Quan Lai ◽  
Guat Ling Lim ◽  
Joel Jia Wei Heng ◽  
Lan Guo ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Fluid Mechanics ◽  
Animal Studies ◽  
Shear Stresses ◽  
Complex Flow ◽  
Congenital Heart Malformations ◽  
Wall Shear ◽  
Dynamics Simulations

There are 0.6–1.9% of US children who were born with congenital heart malformations. Clinical and animal studies suggest that abnormal blood flow forces might play a role in causing these malformation, highlighting the importance of understanding the fetal cardiovascular fluid mechanics. We performed computational fluid dynamics simulations of the right ventricles, based on four-dimensional ultrasound scans of three 20-wk-old normal human fetuses, to characterize their flow and energy dynamics. Peak intraventricular pressure gradients were found to be 0.2–0.9 mmHg during systole, and 0.1–0.2 mmHg during diastole. Diastolic wall shear stresses were found to be around 1 Pa, which could elevate to 2–4 Pa during systole in the outflow tract. Fetal right ventricles have complex flow patterns featuring two interacting diastolic vortex rings, formed during diastolic E wave and A wave. These rings persisted through the end of systole and elevated wall shear stresses in their proximity. They were observed to conserve ∼25.0% of peak diastolic kinetic energy to be carried over into the subsequent systole. However, this carried-over kinetic energy did not significantly alter the work done by the heart for ejection. Thus, while diastolic vortexes played a significant role in determining spatial patterns and magnitudes of diastolic wall shear stresses, they did not have significant influence on systolic ejection. Our results can serve as a baseline for future comparison with diseased hearts.

scholarly journals Computational fluid dynamics simulation as a tool for optimizing the hydrodynamic performance of membrane bioreactors

RSC Advances ◽  
2019 ◽  
Vol 9 (55) ◽  
pp. 32034-32046 ◽  
Author(s):  
Yan Jin ◽  
Cheng-Lin Liu ◽  
Xing-Fu Song ◽  
Jian-Guo Yu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Membrane Bioreactors ◽  
Dynamics Simulation ◽  
Hydrodynamic Performance ◽  
Shear Stresses ◽  
Computational Fluid Dynamics Simulation ◽  
Hydrodynamic Properties

The hydrodynamic properties and shear stresses experienced by a membrane bioreactor (MBR) are directly related to its rate of membrane fouling.

scholarly journals Numerical model of self-propulsion in a fluid

2005 ◽  
Vol 2 (2) ◽  
pp. 79-88 ◽  
Author(s):  
D.J.J Farnell ◽  
T David ◽  
D.C Barton
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Lateral Displacement ◽  
Leading Edge ◽  
Mechanical Device ◽  
Lagrange Equations ◽  
Weakly Coupled

We provide initial evidence that a structure formed from an articulated series of linked elements, where each element has a given stiffness, damping and driving term with respect to its neighbours, may ‘swim’ through a fluid under certain conditions. We derive a Lagrangian for this system and, in particular, we note that we allow the leading edge to move along the x -axis. We assume that no lateral displacement of the leading edge of the structure is possible, although head ‘yaw’ is allowed. The fluid is simulated using a computational fluid dynamics technique, and we are able to determine and solve Euler–Lagrange equations for the structure. These two calculations are solved simultaneously by using a weakly coupled solver. We illustrate our method by showing that we are able to induce both forward and backward swimming. A discussion of the relevance of these simulations to a slowly swimming body, such as a mechanical device or a fish, is given.

Computational Fluid Dynamics Analysis of Two Parallel Rectangular Jets Using OpenFOAM

2016 ◽  
Author(s):  
Han Li ◽  
Huhu Wang ◽  
Yassin A. Hassan ◽  
N. K. Anand
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulent Flow ◽  
Stokes Equations ◽  
Laser Doppler Anemometry ◽  
Physical Models ◽  
Shear Stresses ◽  
Turbulence Characteristic ◽  
Computational Fluid Dynamics Analysis ◽  
Simulation Results

Two or multiple parallel jets are an important shear flow that widely existing in many industrial applications. The interaction between turbulence jets enables fast and thorough mixing of two fluids. The mixing feature of parallel jets has many engineering applications, such as, in Generation IV conceptual nuclear reactors, the coolants merge in upper or lower plenum after passing through the reactor core. While study of parallel jets mixing phenomenon, numerical experiments such as Computational Fluid Dynamics (CFD) simulations are extensively incorporated. Validation of varied turbulent models is of importance to make sure that the numerical results could be trusted and served as a guideline further design purpose. Many commercial CFD packages in the market such as FLUENT and Star CCM+ can provide the ability to simulate turbulent flow with predefined turbulence model, however, such commercial solvers may lack the flexibility that allow users build their own models for R&D purpose. The existing solvers in OpenFOAM are developed to fulfill both academic and industrial needs by achieving large-scale computational capability with a variety of physical models. Moreover, as an open source CFD toolbox, OpenFOAM grants users full control of the source code with complete freedom of customization. The purpose of this study is to perform CFD simulation using OpenFOAM for two submerged parallel jets issuing from two rectangular channels. Fully hexahedron multi-density mesh is generated using blockMesh utility to ensure velocity gradients are properly evaluated. A generalized-multi-grid solver is used to enhance convergence. Based on Reynolds-Averaged Navier-Stokes Equations (RANS), the realizable k-ε and k-ε shear stress transport (SST) are selected to model turbulent flow. Steady state Finite Volume solver simpleFoam is used to perform the simulation. In addition, data from experiments run in Thermal-Hydraulic Lab at Texas A&M University using particle image velocity (PIV) and Laser Doppler Anemometry (LDA) methods are considered in order to compare and validate simulation results. A number of turbulence characteristic such as mean velocities, turbulent intensities, z-component vorticity were compared with experiments. It was found that for stream-wise mean velocity profile as well as shear stresses, the realizable k-ε model exhibits a good agreement with experimental data. However, velocity fluctuation and turbulence intensities, simulation results showed a certain discrepancy.

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