Alpine introduced a significant upgrade package for Imola, consisting of a new front wing, nose and floor, and this was supported by a revised diffuser for Portimao. Overall, the team performed well at a circuit where it struggled just six months before, suggesting that a genuine step forward in performance may have been made, as opposed to the improvement being circuit-specific.
The development to the diffuser concerned the outboard of the three fences employed, with a reduction in its overall height, together with the removal of the slots in the old version. Removing the slots should increase the load of the fence, but make it more prone to phenomena such as flow separation or vortex breakdown. However, trimming the fence will reduce its load, countering these negative aspects. Overall therefore, the load may be similar, but the raised tip will lift the vortex that is shed.
This may be designed to have a local effect or a more global one. Locally, raising the vortex will move it closer to the underside of the diffuser, thereby increasing the suction here. More globally, at low rear ride height (for instance in high speed corners), the vortices in the diffuser become very loaded, and it is important to not only consider their behaviour close to the car, but also far downstream. It is vital to minimise blockage further back, thereby increasing the mass flow under the diffuser. This blockage is, in part, caused by the interaction of these loaded vortices, and by altering their position, improvements can be made.
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