In March 2018 Rimac presented its new electric sportscar, the C_Two. Testing the powerful and technologically advanced hypercar required various methods, tools and processes.
Designed from scratch, the GT was engineered in just over two years. To develop the car’s aero package, the team started from a closed body in 2D, moving to 3D analysis using CFD simulation. For this they were able to use the BURA supercomputer at the University of Rijeka in Croatia, which has nearly 7,000 cores. Hundreds of iterations, different strategies and geometries were evaluated virtually. Since the initial design, every surface evolved numerous times.
Before the tooling stage, the vehicle was tested in the wind tunnel and the results correlated with simulation. A full-scale C_Two model was built specifically for the wind tunnel featuring fully functional active aero components, realistic suspension and brakes, fans, realistic pressure drop across the radiator cores and the rotating wheels. This enabled the team to test the relevant parts quickly and compare the results to CFD.
Wind tunnel analysis was conducted in sessions, each focusing on a different area: drag coefficient, lift coefficient, and cooling efficiency. The CFD results were very close to the experimental results – for example the average deviation between simulation and wind tunnel testing for drag coefficient was only 2.4%. Rimac notes that it is very important to merge the CFD results with wind tunnel measurements and track testing, which is vital to gain subjective feedback on the car.
