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Due to the energy crisis, one of the important challenges in the Auto industry is to reduce the fuel consumption of the vehicle. And the higher speed is, the more fuel consumption is taken by the aerodynamic drag. Mostly, the aerodynamic drag lies on the shape of the vehicle. Consequently, the improvement of the aerodynamics of vehicle shape, more precisely the reduction of their aerodynamic drag, becomes one of the main topics of the automotive researchers. For a container-truck, the three dimensions of the container are standard and unchanged, and the shape of cab is almost fixed by the aesthetic sculpt. For those container-trucks, aerodynamic additional equipments can decrease the aerodynamic drag evidently, especially the wind deflector. Accordingly, this paper describes a method which combines CAD, CFD, Approximate model and optimization carried out on the aerodynamic shape of a container-truck's wind deflector.

Realizable k-ε turbulence model has been used widely for engineering development. In this turbulence model, the default values of empirical coefficients such as C₂, σk and σε are obtained from some particular experiments. They are a good choice for most simulations-though may be not the best choice for simulating the aerodynamic characteristics of road vehicle. In order to improve the accuracy of simulation, a set of new empirical coefficients should be designed especially for simulating the aerodynamic characteristics of road vehicle. These empirical coefficients are found out by DoE (design of experiments) in this paper. Firstly the value range of empirical coefficients is decided by the laws that the aerodynamic force coefficients change with altering of empirical coefficients. Secondly 20 sets of empirical coefficients are obtained randomly by applying optimal Latin Hypercube method in Isight.