CFD simulation and validation of a formula student car

Abstract

The generation of downforce is achieved with aerodynamic devices and nowadays it is one of the most important performance targets, which makes the difference between winning and losing. By means of TU Wien Racing’s 2022/23 Formula Student contender, the EDGE 14, the CFD simulation of aerodynamic components will be analysed in terms of accuracy, quality and magnitude of results. TU Wien Racing conducts all CFD simulations in Siemens StarCCM+. This is where a straightline halfcar simulation is implemented using the EDGE 14 CAD geometry. After generating a domain to calculate the flow and assigning the surfaces to boundary conditions, a turbulence model is chosen. The k-ω model is state of the art in external aerodynamic calculations and therefore used in this application. For the discretization of the fluid, the finite volume method is chosen in combination with the so-called Trimmed Cell Mesher. After explaining where and why to use the high wall y+ approach or low wall y+ approach, a mesh refinement study is conducted. Therefore the CLA and CDA values for an infinitesimal small grid resolution using Richardson Extrapolation are calculated. The validation of these values has been done by continually refining the mesh until CLA and CDA did not change any more and mesh independence was achieved. Validation of the CFD simulation results were carried out with local pressure measurements. Therefore the absolute pressure at 61 measurement points behind the front tyre has been obtained using an aero rake. These values were used to calculate the total pressure coefficient and compare it to the simulation results. The results were satisfying and only small differences were detected. Additionally, validation using pressure taps has been carried out. 8 probes measured the surface pressure on the low pressure side of the undertray mainfoil and these results were again compared to CFD simulation results. Finally, it has been proven that the magnitude of output by the CFD simulation is higher than in real life.