Effects of Rear Slant Angles on the Flow Characteristics of the Ahmed Body by IDDES Simulations

Paper #:
  • 2018-01-0720

Published:
  • 2018-04-03
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Abstract:
The present study aims to investigate the effects of the rear slant angles, j = 25°, 30°, 32° and 35°, on the wake characteristics downstream of the Ahmed body because the angle of the rear window plays an important role in the flow characteristics. This work presents numerical simulations using ISIS-CFD flow solver which is developed by Centrale Nantes and CNRS. The turbulence model used is an hybrid RANS-LES model: the Improved Delayed Detached Eddy Simulation (IDDES). Detailed discussions of the flow features are provided using time-averaged streamlines, vorticity contours, turbulent kinetic energy contours ans an iso-surface of l2. Drag and lift coefficients are also presented. Three crtitical flow points, which correspond to foci of separation and saddle point in the wake of the Ahmed body, in the symmetry plane, are presented. When the slant angle increases, these critical points move near the Ahed body before moving away the model when the slant angle is higher than 32°. For the slant angle j = 35°, a low drag configuration is predicted while for the other slant angles, a high drag flow configuration is predicted where two C-pillars vortex are present. These vortices move away the model when the slant angle increases. The comparison with experimental data are in good agreement.
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