Computational Study of the Wake Structure of a Simplified Ground-vehicle Shape with Base Slant

Three-dimensional flows around a vehicle-like bluff body (Ahmed's body) in ground proximity were computed by directly integrating the governing unsteady, incompressible Navier-Stokes equations. A well-established finite-difference procedure was used. The basic equations were formulated in a generalized coordinate system. A third-order upwind scheme was applied to discretize the equations, and the numerical solutions were acquired without any explicit turbulence models. Computations were performed at a high Reynolds number, Re=10⁶ (based on the body length). In order to investigate the influence of the base slant angle, computations were performed for three base slant angles, i.e., 12.5 °, 25 °and 30 °. Extensive flow visualizations, using state-of-the-art computer graphics, were carried out.

The present numerical results were found to be in broad agreement with the experiments of Ahmed. The present numerical solutions successfully captured the essential features of the flow, especially for the case of a high-drag stage.

The computations were carried out on a supercomputer NEC SX-1 of 570 MFLOPS.