bot6 wrote:I think it also helps to isolate the diffuser itself from the turbulence caused by the spinning rear wheels. It might not be the main effect, but it certainly would help diffuser efficiency.
Also, if you look at the angle of those fins compared to the fences in the diffuser, the "cheese grater" seems to be accompanying the flow out of the diffuser more than really turning it. Considering the chord and span of those little foils, I doubt they have enough area to effectively change the direction of the flow, which is why I think they are mostly there to guide and stabilise rather than bend the airflow.
They are to high to only serve as diff extension.
Small surface area, but multiple elements and quite big angle of attack - i think one can expect significant change of flow direction.
4 purposes IMO:
- filling the void behind rear tyre helps with drag
- low pressure/high speed area on the inside directs diff vortexes outside and connects to one of 2 strong vortexes behind the tyre (aerodynamic diff sidewall extension, sort of)
- strong vortex created at lower tips seals diff to some extend in vertical plane and is low pressure, which helps further with diff efficiency.
- pressing both vortexes behind rear tyre to the outside.
Draggy, but must be worth it.