Comparisons of the Aerodynamic Performance of two Silver Arrows from the Thirties

Abstract

In the 1930’s, the motor sport was dominated by the German manufacturers Auto Union (today Audi) and Mercedes-­‐Benz. Their unique cars, known as the Silver Arrows due to their visible surface of aluminium, were then by far the most outstanding race cars at the Grand Prix. Their cutting edge technology provided great striking power and even today, engineers are astonished by their feat of engineering. A Bachelor thesis from 2013 was carried out to model and to simulate two Silver Arrows (Auto Union Type C and Mercedes-­‐Benz W25) in a commercial CFD software. At the time, previous CAD data were not available for the cars, thus the models were created from scratch using two CMC models in scale 1:18. The thesis reports that the large time consumption required for the CAD modelling accompanied that the work of the simulations could not be performed as desired. The purpose of the 2014 thesis was to improve the existing flow analysis of the Silver Arrows. It was done by improving the above mentioned CAD models and to execute new, more reliable simulations of these; at different speeds and angles of the cars. This project is based on a standard procedure for any CFD process; with a three-­‐module workflow. The initial stage was pre-­‐processing, where the previous year’s CAD models were refined in CATIA V5. For instance, both engine blocks and parts on the cars surfaces were modified to create two more realistic models of the Silver Arrows. The complete CAD models were then processed in ANSA where a surface mesh was generated and then imported into STAR-­‐CCM+. In STAR-­‐CCM+ a virtual wind tunnel was created and a full volume mesh was generated. The second stage was solving in STAR-­‐CCM+ by performing a number of simulations. A total of 23 simulations were completed with different angles and different velocities of the cars. In the final and third stage, the post-­‐processing was performed by analysing and visualizing the results of the completed simulations. By creating a number of different scenes per simulation, the changes in pressure and velocity among others could be visualized. The simulations show that the Silver Arrows are relatively well designed in an aerodynamic perspective, which mainly applies to the Mercedes-­‐Benz W25. The Auto Union Type C has a much higher drag force in comparison. The cars exhibit none or almost no negative lift force, which can be expected, considered as knowledge about its significance was minor. The conclusion is that the Mercedes-­‐Benz W25 is better designed in an aerodynamic perspective regardless of angles or speed of the cars. Overall, the project has proceeded according to plan. Out of the 24 simulations that were wished to conduct, 23 received reliable results. In essence, all objectives have been answered.