Efficient Use of Computational Fluid Dynamics for the Aerodynamic Development Process in the Automotive Industry

Abstract

This paper presents results of the work on the validation and optimization of a Computational Fluid Dynamics (CFD) method used as a development tool, and on the integration of the CFD simulation in the development process. For validation purposes, simulations of air flows around the well known Ahmed body and the SAE Notchback Reference model, as well as a detailed 1:4 car model, have been carried out. Finally, the method is used to predict the aerodynamic forces on a real vehicle. The applied CFD method yielded good results for the academic examples, but when applying the method to industrial flows, deviations from measurement results are observed. The reasons may be, on the one hand, a weakness of CFD in predicting flow separation accurately, but, on the other hand, also the strong dependency of measurement results on the wind tunnel used. As a consequence, MAGNA STEYR does not use CFD for the validation of wind tunnel tests in the aerodynamic development process, but rather for active development and optimization. The paper shows that the effect of a modified vehicle shape with regard to drag and lift can be predicted with CFD, without the need to perform wind tunnel tests.