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Research Papers: Flows in Complex Systems

Separated Flows Around the Rear Window of a Simplified Car Geometry

[+] Author and Article Information
Mathieu Rouméas

 Groupe “Mécanique des Fluides et Aérodynamique,” Direction de la Recherche Renault, 1 Avenue du Golf (TCR AVA 058), 78288 Guyancourt, Francemathieu.roumeas@yahoo.fr

Patrick Gilliéron

 Groupe “Mécanique des Fluides et Aérodynamique,” Direction de la Recherche Renault, 1 Avenue du Golf (TCR AVA 058), 78288 Guyancourt, Francepatrick.gillieron@renault.com

Azeddine Kourta

 Institut de Mécanique des Fluides de Toulouse, Groupe EMT2, Avenue du Professeur Camille Soula, 31400 Toulouse, Francekourta@imft.fr

J. Fluids Eng 130(2), 021101 (Jan 24, 2008) (10 pages) doi:10.1115/1.2829566 History: Received July 27, 2006; Revised August 30, 2007; Published January 24, 2008

A 3D numerical simulation based on the lattice Boltzmann method is carried out on a simplified car geometry (initially proposed by Ahmed, Ramm, and Falting, 1984, SAE Technical Paper series No. 840300) to analyze and establish a method for controlling the near-wake flow topology of a generic blunt body model. The results indicate the existence of a complex flow topology consisting of transverse and longitudinal vortices emanating from flow separations that occur on the top and the lateral edges of the slanted rear window, respectively. The topology of each structure is detailed and the numerical results are compared with the experimental results in the literature. The results presented in this paper can then be used to develop and parametrize active control solutions conducive to improving the aerodynamic performances of automobile vehicles.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Definition of a velocity lattice with 34 velocities on three energy levels (▵, Level 0; ○, Level 1; and ●, Level 2), Chen (15)

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Figure 2

Schematic of the numerical simulation setup: (a) studied geometry and (b) simulation volume

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Figure 3

Schematic of the volume mesh distribution around the geometry: (a) block B2 perspective, (b) cross section in longitudinal plane P1 situated on left-hand side edge, and (c) cross section in longitudinal median plane P2 on upper edge of rear window

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Figure 4

Near-wake flow topology: (a) isosurface Cpi=1.22 and (b) total pressure loss field measured in transverse Plane 1 (defined in (a))

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Figure 5

Definition of measurement planes on rear window and end of roof

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Figure 6

Longitudinal velocity profiles in the vertical direction measured in longitudinal median plane

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Figure 7

Friction line traces noted on left-hand part of rear window: (a) present numerical results and (b) experimental results, Gilliéron (22)

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Figure 8

Definition measurement planes

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Figure 9

Vorticity fields measured in transverse planes located on longitudinal vortex T2 for various coordinate: (a) x1∕l=0.25, (b) x1∕l=0.45, (c) x1∕l=0.63, and (d) x1∕l=0.95

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Figure 10

Static pressure loss coefficient fields measured in transverse planes located on longitudinal vortex T2 for various coordinate: (a) x1∕l=0.25, (b) x1∕l=0.45, (c) x1∕l=0.63, and (d) x1∕l=0.95

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Figure 11

Vorticity isocontour surface (ω=104s−1): (a) definition of coordinate system associated with vortex T2, and (b) determination of vortex axis position with respect to rear window

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Figure 12

Velocity profiles in the longitudinal left-hand vortex T2 for different coordinates: (a) axial velocity transverse profile Vx2(y2=0,z2), (b) schematic diagram of jet and wake-type vortices, (c) azimuthal velocity profile in the transverse direction (Vy2(y2=0,z2)), and (d) azimuthal velocity transverse profile in the vertical direction (Vz2(y2,z2=0))

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