Numerical simulation of the influence of a passive drag reduction device applied to ahmed’s squared-back model at the industrial scale

Abstract

A passive drag control device can obtain the increase in energy efficiency of automobiles. Chamfers in edges of the vertical base are an effective reduction drag technique employed to squared-back cars. Still, the changes in the vehicle shape in the last stages of design process are discouraged. Therefore, chamfers optimization research in the early cycles of a new model’s development by a computational simulation becomes attractive.

Thus, the aim of this study is to validate a computational model that could be used to study chamfers aerodynamics affects at squared-back vehicle, at Re of 106 order. For this purpose, numerical evaluation of the Ahmed’s squaredback model at the industrial scale, at a Reynolds number of 2.26 million, were done. A specific configuration of short chamfers was tested. Simulations based on Unsteady Reynolds-Averaged Navier-Stokes and the k-? SST turbulence model were done. The method was satisfactory. The simulations reproduced the mean organization of the flow at the near wake to the original model and identified spectral activity of the recirculation bubble with ??ு between 0.11 and 0.14. The mean drag coefficient of the model was overestimated by 5.7% the reference experiment data. The use of chamfers in the model’s base reduced the length and cross section area of the recirculation bubble. Changes in the wake’s spectral activity and the appearance of longitudinal vortices originated at the lateral edges of the chamfers were observed as well. The modified model experienced a drag coefficient reduction in the order of 2.7% compared to the original model.