A ground effect floor on a car that had never successfully run one.
The 2025 car ran no floor, so all downforce was generated by the wings at a significant drag cost. I designed a full ground effect undertray with venturi tunnels, barge board flow directors, and a rear diffuser, and ran it in STAR-CCM+ on the university supercomputer with meshes exceeding 100 million cells. Simulations used RANS with SST k-omega turbulence modeling to predict boundary layer separation across the high lift surfaces. Design iteration focused on diffuser angle, strake sizing, and ride height. Barge boards outwash the front tire wake before it reaches the tunnels, and the tunnels extend past the leading edge of the rear tires to use the full legal floor area.
Ground effect performance is highly ride height sensitive, so geometry optimized at a single fixed height does not hold on a car that pitches under braking and rolls in a corner. I weighted the study across the ride height range the car operates in, trading peak downforce for consistency. The floor also added 9 lbs to a 463 lb car. Improved layup technique reduced the net package weight increase to 6 lbs, and the floor lowered CG from 12.56 in to 12.29 in, offsetting part of the mass penalty.
The undertray produces 1.15 Cl at 0.09 Cd, up from zero. Full package Cl increased from 2.17 to 3.48, a 60% gain, while Cd rose only from 0.89 to 1.09. The same package increased radiator mass flow from 0.077 to 0.112 kg/s, reducing peak oil temperature by 8F and peak water temperature by 14F.