Aerodynamic Drag Reduction of Vehicle Based on Free Form Deformation

Abstract

At present, the most common approach for vehicle aerodynamic drag reduction is trial and error method, which completely depended on the engineers' experience. Inevitably, this method is certain blindness and low efficiency. Moreover, it is quite difficult to parametrize the auto body in the aerodynamic optimization design. To solve these problems, a fast and effective parametrization method named free form deformation (FFD) is introduced into the vehicle aerodynamic optimization design. Firstly, selecting a car model as the simulation object, sample space is constructed based on the optimal Latin hypercube experiment design, and FFD method is used to parameterize the model of each sample point. Secondly, the aerodynamic drag coefficient of each sample is obtained by CFD simulation. Then, according to the sample space and computational results obtained by CFD, Kriging model is selected to build the approximate model. Finally, the multi-island genetic algorithm is employed to get the optimal combination of the design variables. To validate the reliability of the final results, a new model is reconstructed according to the results of the optimization, and aerodynamic drag coefficient is computed by CFD again. The computational results show that the car model aerodynamic drag coefficient has decreased by 4.09% after optimization, which confirms that FFD method deserves to be popularized in vehicle aerodynamic optimization design.