Optimization Procedure in a Car Aerodynamic Design: Examples of Application with CFD

Abstract

In the initial phase of a car project, difficulties arise from the high number of parameters involved. A systematic aerodynamic analysis taking into account the effects of all these parameters appears to be difficult, given the complexity related to both aerodynamic load evaluation and the assessment of general requirements of the car. In the analysis through numerical optimization, an aerodynamic code is coupled in a loop with an optimization routine, to automatically manage the values of the design variables, with the aim of minimizing a given objective function. This approach is extremely flexible, and capable of meeting multi-disciplinary requirements. Therefore, in the past, it was developed an advanced, integrated design and development environment for optimizing car aerodynamics, under certain geometrical and physical constraints imposed by the designer. A potential flow code was used initially; obviously, the capabilities of this model are restricted. The important increases in both the CFD algorithms and computing capabilities, suggested the possibility to use RANS solver in the optimisation procedure. Therefore, an activity to insert in the procedure a CFD code (FLUENT) was carried out. The process is driven by the code ModeFrontier, and it can now be considered a standard tool in aerodynamic design. In this paper the general scheme of the procedure is described, and an example of the capability to improve the aerodynamic characteristics of a high performance car is presented. By using this approach, increases in the results are obtained both in the initial phase of the project, the definition of the car shape, and in the final phase, in order to optimize the details.