A Navier-Stokes Analysis of Three-Dimensional Turbulent Flows around a Bluff Body in Ground Proximity

The Reynolds-averaged Navier-Stokes equations, together with the equations of the k-E model of turbulence, were solved numerically in a general curvilinear coordinate system for three-dimensional turbulent flows around Ahmed's vehicle-like body. The numerical computations were performed for various afterbody upper-surface slant angles at a constant Reynolds number of 4.3 million based on the body length. Computations were performed with up to a half million grid points by using an external solid-state storage device to supplement limited computer core memory. Most of the essential measured features of the flow field around Ahmed's vehicle-like body in ground proximity, such as the formation of trailing vortices and the reverse flow region resulting from separation, were well predicted. In spite of the extreme complexity of the flow field, the effects of afterbody slant angle on the aerodynamic drag were correctly predicted, except near the critical angle. Near the critical angle, improvement of the turbulence model appears to be necessary.

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