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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 4 th year - Biomedical Engineering Faculty Mentor: Dr. Urmila Ghia Department of Mechanical and Materials Engineering. NSF Type 1 STEP Grant, Grant ID No.: DUE-0756921.

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Project #4: Simulation of Fluid Flow in the Screen-Bounded Channel in a Fiber Separator

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  1. 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

  2. Outline • Motivation • Introduction to Bauer McNett Classifier (separator) • Problem Description • Goals & Objectives • Methodology • Verification Case • Porous Boundary Model • Future Work 1

  3. 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 2

  4. = deep open channel Background – Bauer McNett Classifier (BMC) Open to atmosphere • 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 Wire Screen B A C AL 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 Figure 3: Top View of One BMC Tank 3

  5. Background – Bauer McNett Classifier (BMC) Figure 4:Fibers parallel to screen Figure 5:Fibers perpendicular to screen Off-plane angle 0° Off-plane angle 90° 4 Fibers length larger than mesh opening Fibers length smaller than mesh opening

  6. 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 Figure 6: General Dimensions screen Figure 7: Porous Model Dimensions

  7. Goals and Objectives Goal: Numerically study the fluid flow in a deep open channel Objectives: a) Verify boundary conditions and variables of the porous model • Simplified porous plate problemasverification case b) Simulate and study the flow in the open channel of the BMC apparatus, modeling the screen as a porous boundary c) Determine the orientation of shear stress vector on the porous boundary

  8. Methodology Computational Grid • 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 Figure 8: Porous Model Channel Geometry in FLUENT Table 1: Distribution of grid points and smallest spacing near boundaries

  9. 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 Solid Wall Model Porous Boundary Model Figure 9: Boundary Conditions 8 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 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] Outlet, pstat = 0

  10. 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 Figure 10: Laminar Flow Across Porous Flat Plate 9

  11. Verification Case - Boundary Conditions (1 of 2) Case #1: All Solid Walls Case #2: Two Walls, One Pressure Outlet 10

  12. Verification Case - Boundary Conditions (2of 2) Case #3: One Wall and Two Pressure Outlets Case #4: All Pressure Outlets 11

  13. 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 • Conclusion: • All cases show a boundary layer and flow crossing the porous plate 12

  14. Verification Case - Streamlines for Case #1: All Walls

  15. VerificationCase – Darcy’s Law 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. 13

  16. 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 Velocity on Central Plane 14

  17. 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 15

  18. 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 16

  19. 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 17

  20. Appendix: Porous Plate Calculation • Darcy’s Law pressure drop calculations: 18

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