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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 • Flow Caracteristics • Experimental Results • CFD Results • Applications
I. Flow Caracteristics Flow around a cylinder
I. Flow Caracteristics • Effects of Ground Reduces periodical structures
I. Flow Caracteristics • - Effects of Rotation Separation point 25° foward • 3D Effects Uptream jets Stationary wheel Rotating wheel
II. Experimental Flows - Effects of Rotation Reduces Lift, Increases Drag Pressure Distribution Experiment by Cogotti
II. Experimental Flows Lift and Drag Similar distribution Peak at contact point Pressure Distribution 2 1
II. Experimental Flows Wake Experiment by Cogotti
II. Experimental Flows Experimental limitations
III. CFD Viscous Models K-E : good Drag prediction, bad separation point angle Reynolds Stress :bad Drag coefficient, good separation point angle
III. CFD Viscous Models Cp : Pressure distribution from Reynolds stress model matches with Fackrell experiment
III. CFD Grid & Model 3D Grid Solver : Fluent Incompressible air Unsteady T.I. = 0.25% K-E model
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
III. CFD Lift and Drag Drag : good agreement Lift : large discepancy
III. CFD Pressure distribution High Pressure upstream Zone of Low Pressure above and below
III. CFD Wake Large wake area and recirculation zones above and below Separation point is 15° further back than shown by Fackrell
III. CFD Wake Separation point : 3D effects CFD Voticity mathches with Cogotti’s prediction
IV. Automotive Applications Reduce Drag Forces in Futur Vehicules Wake Mirrors Underbody Grill
IV. Automotive Applications Reduce Drag Forces in Futur Vehicules Wheels
IV. Automotive Applications Droplet dispersion
IV. Automotive Applications Droplet dispersion - with fairing Pathlines of droplet with diameter 1 E-4 Pathlines of droplet with diameter 1 E-5
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