Flow structure around a 3D bluff body in ground proximity: A computational study

Abstract

A computational model is developed to help the automotive design engineer to optimize the body shape with minimum wind tunnel testing. Unsteady, Reynolds-averaged, Navier-Stokes equations are solved numerically by a finite-volume method and applied to study the flow around GM's vehicle-like body. The standard k-ϵ model is employed to model the turbulence in the flow. The finite volume equations are formulated in a strong conservative form on a three-dimensional, unstructured grid system. The resulting equations are then solved by an implicit, time marching, pressure-correction based algorithm. The steady state solution is obtained by taking sufficient time steps until the flow field ceases to change with time within a prescribed tolerance. For the pressure-correction equation, preconditioned conjugate gradient method is employed to obtain the solution. Most of the essential features of the flow field around a bluff body in ground proximity, such as the formation of trailing vortices and the reverse flow region resulting from separation, were well predicted. In addition, the variation of drag coefficient with Reynold's number per meter faithfully follows the experimentally observed pattern.