Diffuser design on F1 undertrays

[GregLocock]

At the Melbourne Motorshow I noticed that all three of the diffusers on display had curved triangular fins. Are these supposed to initiate the main trailing vortices, or do they have a more mundane purpose- like restricting sideways flow?



Cheers

Greg Locock

 

[seek]

Greg,

The underbody tunnels have large vortices feeding the flow under the car. Those vanes you seem to enhance this effect and are developed experimentally.

I haven't seen any flow visualisations nor lift coefficient results with or without these vanes. Can't help any more than that.

Joe

 

[GregLocock]

I talked to an aerodynamananacist, she says it is likely that (a) they are fin shaped to slow the lateral migration of high pressure air from the sides into the low pressure air in the diffuser, and (b) they are curved to energise the boundary layer, to delay separation. Cheers

Greg Locock

 

[LMP900]

My experience is from wind tunnel testing of small single-seaters and Le Mans cars: I've never had F1-style budgets to do in-depth analysis of the why's and how's. Empirically, strakes (my term for the fins/vanes) have a major effect on the efficiency of a diffuser, whether on the front of an LMP car or the rear of an F3. I think that they do all the following: prevent lateral flow due to transverse pressure differential; reduce the damage from the "bow-wave" of a rotating tyre; and encourage the entrainment of flow by the vortices created by the pressure differential between channels. A fillet radius at the root of the strake can have a significant effect on efficiency.

Andy