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Research Papers: Flows in Complex Systems

Analysis of the Vorticity in the Near Wake of a Station Wagon

[+] Author and Article Information
Omar D. Lopez Mejia

Associate Professor
Department of Mechanical Engineering,
Universidad de los Andes,
Carrera 1 Este #19 A-40,
Bogotá D.C. 1117711, Colombia
e-mail: od.lopez20@uniandes.edu.co

Sergio A. Ardila Gómez

Department of Mechanical Engineering,
Universidad de los Andes,
Carrera 1 Este #19A-40,
Bogotá D.C. 1117711, Colombia
e-mail: sa.ardila10@uniandes.edu.co

David E. Blanco Otero

Department of Mechanical Engineering,
Universidad de los Andes,
Carrera 1 Este #19A-40,
Bogotá D.C. 1117711, Colombia
e-mail: de.blanco225@uniandes.edu.co

Luis E. Muñoz Camargo

Associate Professor
Department of Mechanical Engineering,
Universidad de los Andes,
Carrera 1 Este #19A-40,
Bogotá D.C. 1117711, Colombia
e-mail: lui-muno@uniandes.edu.co

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received December 15, 2015; final manuscript received August 13, 2016; published online November 7, 2016. Editor: Malcolm J. Andrews.

J. Fluids Eng 139(2), 021105 (Nov 07, 2016) (8 pages) Paper No: FE-15-1929; doi: 10.1115/1.4034523 History: Received December 15, 2015; Revised August 13, 2016

A computational study of the turbulent flow around a modified station wagon vehicle is presented in order to predict aerodynamic forces and to understand some details of the near wake. The geometrical model was obtained by a three-dimensional scanning process but excludes some details of the vehicle such as the engine bay, and the underfloor was considered flat. A hybrid mesh (prisms' layers and tetrahedral) was generated with refinements close to the vehicle surface (including the wheels) and the near wake. The simulations were performed in the commercial software ansys fluent at a Reynolds number of 2.7 × 106 based on the wheelbase. Numerical results of the drag coefficient predict values of 0.431 which is considered in fairly good agreement with the experimental result (based on a coastdown test) of 0.404. Contours of velocity, pressure, and eddy viscosity field show some important features of the separated flow in the rear part of the vehicle. A detailed study of the near wake was performed in which the evolution of the vorticity was analyzed in the downstream direction, showing several pairs of counter-rotating vortices generated from the upper part of the A-pillar, wing mirrors, and the fender of the vehicle.

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References

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Figures

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Fig. 1

Scheme of the computational domain (dimensions in m)

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Fig. 2

Generated mesh of the computational domain with boxes of density used for mesh refinement (sizes in mm)

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Fig. 3

Mesh convergence (size in million)

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Fig. 4

Histogram mesh quality (2.7 × 106)

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Fig. 5

Velocity contours in the symmetry plane

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Fig. 6

Pressure contours in (a) the symmetry plane and (b) coefficient of pressure on the vehicle surface

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Fig. 7

Turbulent viscosity contour in the symmetry plane

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Fig. 8

Isosurface of the second invariant of velocity gradient tensor Q

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Fig. 9

Velocity magnitude and streamlines in the symmetry plane

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Fig. 10

Y-vorticity contours and characterization of vortices in the wake at different planes located at: (a) 10 cm, (b) 30 cm, (c) 60 cm, and (d) 80 cm downstream the vehicle

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Fig. 11

Isosurfaces of the second invariant of velocity gradient tensor Q and streamlines colored by vorticity

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Fig. 12

Geometrical characterization of the vortices in the near wake

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