A computational fluid dynamics study of air entrance s influence on the air resistance of ahmed reference body

Abstract

In traditional design and optimization of vehicle’s aerodynamic performance, there are few considering about engine compartment’s influence on vehicle's air resistance. In order to find out the engine compartment’s influence on the air resistance of the whole vehicle, we conducted some simulations. In this study, Ahmed model was applied to find out how the position and the aspect ratio of the air entrance in the front of the vehicle influence the air resistance of vehicles. And the study was performed only in the premise that the open area and the volume of the engine compartment were constant. The simulations were calculated using the RNG k-ε model with Standard Wall Functions which has already been proved to fit Ahmed model very well by a large number of numerical results. Through simulation, the following conclusions have come to eyes:1, When β which means the ratio of the width and height is in the range of 2 to 4, the drag coefficient continuously decreases. That is, the flatter the entrance is, the smaller the drag coefficient would be. 2, the drag coefficient also decreases with the average diameter of porous media in the case that the cab was filled with porous media. However, what can’t be ignored is that small average diameter may cause the shortage of cooling capacity.