A question for the more learned here. The Corvette C6R (GT1) and a number of other cars in this category have rear diffusers with an abundance of vertical fences, more so then any other category car I can think of. Why?
Spanwise flow?
The wide diffuser tray on the #3 Corvette has 14 channels. The three on each end are narrower than the ones inside. If those fences were not in place, air could drift sideways, instead of exiting directly backwards. This could cause the different ends of the tray to have higher or lower downforce than the other. With the fences, downforce is kept equal side to side.
I've been conceptualizing the effects of the vanes in diffusers and they are certainly designed to isolate and straighten flow. Why some use as few as four, and others like the Corvette team use as many as could possibly be fitted, I can only speculate.
The diffuser size is regulated in the class the Corvette runs in, including max width and height and depth. I would think these restrictions have a great deal to do with the reasons some teams use so many strakes/vanes.
It could be that since these sedan based cars spend much of their aero efforts fighting push, and they use rear wings, the rear diffuser is not used soley to generate downforce.
I'm thinking that the strakes/vanes might add stability in a mild oversteer situation, such as full power corner exit. But I don't know for sure. I think anyone that does know for sure is not talking much. I've looked high and low and haven't found any studies that address strakes and vanes in diffusers. While I've found a healthy number of studies on diffuser design none of them tackle the effects of vanes/strakes.
