Automatic Shape Optimization of Aerodynamic Properties of Cars.

Abstract

An automatic shape optimization process with the aim to improve the aerodynamic properties of cars is described in the following sections. The AVL FIRE code is used for mesh generation and CFD calculations. Sculptor is used for mesh deformation and the design environment modeFrontier is used for optimization. The optimization algorithms Simplex and Evolution Strategies, for nonlinear optimization problems, are used to achieve an optimal solution in an automatic optimization process. The rear end of the car is modifed, frst with one parameter, then two. Both single- and multi-objective optimization is performed, minimizing first drag and then both drag and lift. Comparison is made between steady k-epsilon and LES turbulence models resulting in two different optimal geometries. Using k-epsilon drag was reduced by 1.3% with increased lift of 38% while using LES drag was reduced by 13% and lift by 26 %. The process has been shown to work for multi-objective optimization. Other optimization algorithms can be used easily. The process is not restricted to optimization of drag or lift but can be modified to other ow quantities related to e.g. cross-wind stability, aero-acoustics, e.t.c.