Project #4: Simulation of Fluid Flow in the Screen-Bounded Channel in a Fiber Separator
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Transcript of Project #4: Simulation of Fluid Flow in the Screen-Bounded Channel in a Fiber Separator
Project #4: Simulation of Fluid Flow in the Screen-Bounded Channel in a Fiber Separator
Lana Sneath and Sandra Hernandez
4th year - Biomedical Engineering
Faculty Mentor: Dr. Urmila Ghia
Department of Mechanical
and Materials Engineering
NSF Type 1 STEP Grant, Grant ID No.: DUE-0756921
Outline
• Motivation• Introduction to Bauer
McNett Classifier (separator)
• Problem Description• Goals & Objectives
• Methodology• Verification Case• Porous Boundary
Model• Future Work
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Problem Background• Toxicity of asbestos exposure varies with length of
asbestos fibers inhaled• Further study of this effect requires large batches of
fibers classified by length • The Bauer McNett Classifier (BMC) provides a
technology to length-separate fibers in large batches
Figure 1: Bauer McNett Classifier (BMC) Figure 2: Schematic of BMC
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Background – Bauer McNett Classifier (BMC)
• Fiber separation occurs in the deep narrow channel with a wire screen on one side wall
• Fibers align with local shear stress vectors [1]
• For successful length-based separation, the fibers must be parallel to the screen
Open to atmosphere
= deep open channel
Figure 3: Top View of One BMC Tank
A
B
CAL
1. Civelekogle-Scholey, G., Wayne Orr, A., Novak, I., Meister, J.-J., Schwartz, M. A., Mogilner, A. (2005), “Model of coupled transient changes of Rac, Rho, adhesions and stress fibers alignment in endothelial cells responding to shear stress”, Journal of Theoretical Biology, vol 232, p569-585 3
Wire Screen
Background – Bauer McNett Classifier (BMC)
Fibers length smaller than mesh opening
Fibers length larger than mesh opening
Figure 4: Fibers parallel to screen
Figure 5: Fibers perpendicular to screen
Off-plane angle 90°Off-plane angle 0°
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Deep Open Channel Dimensions
General Dimensions:• Length (x) = 0.217 m• Height (y) = 0.2 m• Width (z) = 0.02 m• Aspect ratio = 10; Deep open
channel
Screen dimensions:• Length (x) = 0.1662 m• Height (y) = 0.1746 m• Thickness (z) = 0.0009144 m
screen
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Figure 6: General Dimensions
Figure 7: Porous Model Dimensions
Goals and ObjectivesGoal: Numerically study the fluid flow in a deep open
channelObjectives:a) Verify boundary conditions and variables of the porous model
• Simplified porous plate problemas verification case
b) Simulate and study the flow in the open channel of the BMC apparatus, modeling the screen as a porous boundaryc) Determine the orientation of shear stress vector on the porous boundary
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MethodologyComputational Grid
Figure 8: Porous Model Channel Geometry in FLUENT
Table 1: Distribution of grid points and smallest spacing near boundaries
• Create channel geometry in CFD software
• Generate grid of discrete points
• Determine the proper boundary conditions to model the porous boundary
– Verification case: Laminar flow over a porous plate
• Enter boundary conditions into the CFD software
• Run simulation
• Determine shear stress from flow solutions
• Interpret results
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Boundary Conditions• u, v, w are the x, y, and
z components of velocity, respectively
• Average Inlet Velocity= 0.25m/s
• Turbulent Flow (Reynolds Number >5000)
• Reynolds Stress Model• Transient Simulation
8Figure 9: Boundary Conditions
Free-Slip Wall, v=0, du/dy=0, dw/dy=0
No-Slip Wall, u = v = w = 0
Inlet, u = u(y,z), v = w =0
Outlet, pstat = 0
Porous-Jump, Permeability(K) = 9.6e-10, Pressure-Jump Coefficient(C2)=7610.7 1/m, screen thickness = 9e-4 m; Values correspond to a 16 mesh [5]
Solid Wall Model Porous Boundary Model
Verification Case - Porous Plate Objective
• Determine proper boundary conditions to
use in the Porous Boundary Model case• Verify fluid flow behavior• Observe how axial flow is inhibited by the plate
Methodology:• Create 2D geometry in Gambit
• Calculate Reynolds number for Laminar flow
• Generate grid points• Run simulations in FLUENT
• Run 4 different cases: changing the mesh boundary condition to determine it’s effect
• Interpret results
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Figure 10: Laminar Flow Across Porous Flat Plate
Case #1: All Solid Walls
Case #2:Two Walls, One Pressure Outlet
Verification Case - Boundary Conditions (1 of 2)
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Verification Case - Boundary Conditions (2 of 2)Case #3:
One Wall and Two Pressure OutletsCase #4:All Pressure Outlets
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Verification Case - Velocity Magnitude Contours
Case #1: Velocity Magnitude Contours for All Walls
Case #2:Velocity Magnitude Contours for Two Walls
and One Pressure Outlet
Case #3:Velocity Magnitude Contours for One Wall
and Two Pressure Outlets
Case #4:Velocity Magnitude Contours for All Pressure Outlets
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Conclusion:• All cases show a boundary layer and flow crossing the porous plate
Verification Case - Streamlines for Case #1: All Walls
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Verification Case – Darcy’s LawModel Pressure Drop
Calculated Using Darcy’s Law
Pressure Drop Fluent
Percent Error
All Walls 3.48E-03 3.51781-03 1.19%
Two Walls and One Pressure Outlet
-3.73E-03 -3.679068E-03 1.25%
One Wall and Two Pressure Outlets
2.54E-03 2.53E-03 0.32%
All Pressure Outlet -8.593229E-03 -8.68129E-03 1.01%
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Table 2: Pressure Drop Verification via Darcy’s Law
Conclusion:• Hand calculations were equivalent to FLUENT’s values. • Better understanding how FLUENT uses the porous-jump condition.
Porous Boundary Open Channel - Velocity Magnitude Contours
Figure 11: Isometric View of Axial Variation of Velocity on Central Plane
Figure 12: Front View of Axial Variation of Velocityon Central Plane
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Porous Boundary Open Channel - Shear Stress
Figure 13:Axial Variation of Shear Stress on the Back Wall
at y=0.1 z= 0
Figure 14: Axial Variation of Shear
Stress on Screen at y=0.1 z= 0.02
Figure 15:Axial Variation of Velocity at Line y=0.1, z=0.01
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Future Work• Continue running the porous boundary open
channel model until the fluid flow solution has been calculated for at least 3 minutes to achieve a steady state solution
• Investigate reasoning behind the zero shear stress at the porous boundary
• Compare verification case results for pressure drop calculations to literature
• Interpret results further
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Acknowledgements
• Dr. Ghia for being an excellent faculty mentor and taking the time to make sure we fully understood the concepts behind our research.
• Graduate Students Prahit, Chandrima, Deepak, Nikhil, and Santosh for taking time out of their schedule to teach us the software and help us with any problems we encountered.
• Funding for this research was provided by the NSF CEAS AY REU Program, Part of NSF Type 1 STEP Grant, Grant ID No.: DUE-0756921
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Appendix: Porous Plate Calculation• Darcy’s Law pressure drop calculations:
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