A few teams have a slit/s in their floor to help minimize tyre squirt. Red Bull have now taken this much further with a rather large hole between twin strakes... I think this new development will "open a can of worms" with many teams copying since it's obviously legal.
Trying to better control and direct the plume in to the footstep region. You'll get 2 counter rotating vortices (Aero_A
I think that the aim of the double strake is to have a stronger downwash effect on the exhaust plume in the wheel zone, making the exhusts interact more with the contact patch vortex while keeping the effect on the foot plate vortex.
I try to explain better; let's take as reference the right wheel fo the car, seen from the front.
The ouboard strake, develops a vortex that turns clockwise - the inner strake develops a (weaker? no blocking from rear wheel, just higher pressure from top diffuser ramp) vortex that turns counterclock wise. As a result, in the gap between them, those two vortices induce a vertical downward pointing velocity. The exhausts flow in this gap and are deflected lower than in a configuration with just one vortex.
I think both vortices induce by the two strake will flow in the inner gap between rear wheel and diffuser.
The inner vortex will interact with the footplate vortex (they are more or less aligned and both turning counterclockwise); the exhausts being deflected closer to the ground will be closer to the contact patch vortex.
The contact patch vortex develops between tyre and floor - you can see it in books like Katz or also experimentally measured in the toyota tunnel PIV article by iaccarino and al. that has been linked many times here on the forum.
The exhausts effect will be to accelerate all these vortices along their axis, making pressure much lower as a result (see Gordon McCabe post on helicity I linked some time ago)
