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Flow around a Wheel

Flow around a Wheel. Flow Caracteristics Experimental Results CFD Results Applications. Introduction. I. Flow Caracteristics. Flow around a cylinder. I. Flow Caracteristics. Effects of Ground  Reduces periodical structures. I. Flow Caracteristics.

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Flow around a Wheel

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  1. Flow around a Wheel • Flow Caracteristics • Experimental Results • CFD Results • Applications

  2. Introduction

  3. I. Flow Caracteristics Flow around a cylinder

  4. I. Flow Caracteristics • Effects of Ground  Reduces periodical structures

  5. I. Flow Caracteristics • - Effects of Rotation  Separation point 25° foward • 3D Effects  Uptream jets Stationary wheel Rotating wheel

  6. II. Experimental Flows - Effects of Rotation  Reduces Lift, Increases Drag Pressure Distribution Experiment by Cogotti

  7. II. Experimental Flows Lift and Drag Similar distribution Peak at contact point Pressure Distribution 2 1

  8. II. Experimental Flows Wake Experiment by Cogotti

  9. II. Experimental Flows Experimental limitations

  10. III. CFD Viscous Models K-E : good Drag prediction, bad separation point angle Reynolds Stress :bad Drag coefficient, good separation point angle

  11. III. CFD Viscous Models Cp : Pressure distribution from Reynolds stress model matches with Fackrell experiment

  12. III. CFD Grid & Model 3D Grid Solver : Fluent Incompressible air Unsteady T.I. = 0.25% K-E model

  13. III. CFD Some quick calculations Uo = 7.742m/s D=1m T.I. = 0.25% Let’s assume a stationary wheel : • Re = UD/v = 516,000 • Re(Fackrell) = 530,000 • T.I. = u’/U = 0.25% • U=7.742m/s • u’ = 0.02m/s E = u’^3/L L=D=1m • E = 7.25 E-6 N = (v/E)^1/4 = 5mm

  14. III. CFD Lift and Drag Drag : good agreement Lift : large discepancy

  15. III. CFD Pressure distribution High Pressure upstream Zone of Low Pressure above and below

  16. III. CFD Wake Large wake area and recirculation zones above and below Separation point is 15° further back than shown by Fackrell

  17. III. CFD Wake Separation point : 3D effects CFD Voticity mathches with Cogotti’s prediction

  18. IV. Automotive Applications Reduce Drag Forces in Futur Vehicules Wake Mirrors Underbody Grill

  19. IV. Automotive Applications Reduce Drag Forces in Futur Vehicules Wheels

  20. IV. Automotive Applications Droplet dispersion

  21. IV. Automotive Applications Droplet dispersion - with fairing Pathlines of droplet with diameter 1 E-4 Pathlines of droplet with diameter 1 E-5

  22. References : • - « A CFD Analysis into the effect of Yaw Angle on the Flow around • an isolated rotating wheel » • JONATHAN WRAY, Cranfield University, 2003 • http://public.cranfield.ac.uk/me/me028/rubini/thesis/2003/J.Wray2003.pdf • - « Numerical Simulation of the Air Flow Around a Rotating Wheel » • 3rd MIRA International Vehicles Aerodynamics Conference, 2000 • http://www.cham-swift.com/papers/numerical_sim_air_flow.pdf • - « Reducing Drag Force in Futur Vehicules » Chalmers University, 2002 • http://www.tfd.chalmers.se/~lelo/rvad/reports/rva2002_gr10_drag-reducing.pdf • « A Computational Study of Tandem Dual Wheel Aerodynamics and the effect of fenders and fairings on spray dispersion » • JOHN S. PASCHKEWITZ, Lawrence Livervore National Laboratoiry • http://eed.llnl.gov/aerodrag/pdf/TireSS.pdf

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