mep wrote:Why should the flow there go around a 90° corner?
It has some inertia and high air speed. It will create lots of turbulence for very little flow going trough the hole. I can't see how this should be benefical at all.
thats how static pressure gauges work...
flow from a stream creates a low pressure in the gauge which acts on a diaphragm. the diaphragm acts on a mechanical or piezo electric device thats calibrated to indicate pressure.
In the case of the sauber, the low pressure created by the flow over the bump will be fed buy the high pressure under the nose. This creates a pressure gradient.
I would guess that they want to reattach the boundary layer as it flows over the hump at high speed to reduce drag. Probably a small effect and not a game changer but it potentially works with the cockpit to keep flow attached around the cockpit and over the sidepods to increase effectiveness of the exhaust by maintaining a high pressure above the exhaust pipe exits.
Perhaps this maintains the Coanda effect across a wider speed range.