F1 technical focus
The brake-duct sizing is a compromise. You generate most heat in the brake by braking from high speed to low speed, so you need decent airflow at low speed. But it will not be able to take all that volume of air at high speed and the excess will spill around the outer surface.
This small turning vane just behind the actual brake-cooling inlet will just be managing the excess airflow that comes around the outer surface of the duct.
The lower horizontal turning vane, which in effect puts an endplate on the vertical turning vane it’s attached to, gives a more consistent airflow coming off the trailing edge of that component – especially with varying steering lock.
SMALL BRAKE DUCT TURNING VANE (INSET NORMAL)