Numerical Study on Aerodynamic Drag Reduction on a Rear Wing of a Formula Student Car

Sammanfattning: The importance of aerodynamics in racing has increased substantially over the past decades. Racing vehicles utilize different aerodynamic devices, to redirect the airflow around the vehicle in a beneficial way. The increase in downforce using an aerodynamic wing package increases drag force. The drag force limits the top speed and the maximum acceleration of the vehicle and is an unwanted effect of increased downforce. To combat this, top-performance vehicles utilize a drag reduction system (DRS). The DRS is an active system of the vehicle, which allows adjustment of the angle of attack (AoA) of wings on the vehicle while driving on track when deemed beneficial. This thesis will investigate the possibility of adding a DRS to the rear wing of a Formula Student vehicle. All tests were done by simulations, no physical tests were done in this thesis. The investigation of a DRS was done in three stages. The first step was to create a 3-dimensional CAD-model that complied with the Formula Student Germany rules. The design of the rear wing was based on the current rear wing on the KTH Formula Student vehicle. The current rear wing was slightly redesigned for this project to facilitate the investigation of a DRS. The second step was to create a mesh model. A mesh is a representation of a geometry, it defines the physical shape of an object, in this case the rear wing. The more detailed a mesh is, with a higher number of cells, the more accurate the results will be from the simulations. However, a finer mesh with a high number of cells increases the simulation time significantly. Therefore, it is important to find a good balance between the number of cells and the time it takes to make a simulation. After a mesh was generated, physics models for the simulation were determined. The final step was to make simulations based on the physics models chosen. For this project, Siemens NX was used to design a three-dimensional model of the wing and Siemens STAR-CCM+ was used to make the simulations and meshes.  The resulting reduction in drag was calculated to 78 per cent between the closed configuration and the open configuration with the least drag. However, there is a large amount of separation between the airflow and the rear wing on all configurations simulated except at the AoA -10°. When the airflow separates downforce decreases and drag increases and is not desirable.  The drag on the rear wing can be decreased by utilizing a DRS as observed from the results. The drag reduced by the DRS at 15° and -10° AoA and a DRS would certainly be beneficial. Further investigation of computational fluid dynamics and aerodynamics is recommended to complement the result. There are uncertainties in the results due to inadequacy in the mesh and design of the rear wing. By addressing these uncertainties better results can be achieved.