Bonnet bra aero

[Rosieuk]

Got my hands on one of these today (in between prescription and Tegu wrangling) and something struck me as odd.
The back edge of the upper panel has what I'd describe as two ears (presumably airflow hold downs) but it strikes me that if you look up the line of flow towards the windscreen wipers, the two ears (perpendicular triangular spoilers about an inch high and maybe 6in wide) might act to channel the airflow around and over the exposed wiper mounts (thank you Hyundai).
I dont know if I'm going to fit this yet, I'm not even sure if I'll even get a working car back - but it strikes me that if this is the case for certain cars, you'd get an aerodynamic benefit as well as protection from road edge gravel and stones helpfully sprayed by uncoordinated cretins (although not the head sized rock that was spat out of an artic wheel and almost decapitated my dad (that was one sad looking Mercedes estate)).
I wondered if anyone had previously tested or thought of testing this theory? The things look not a little like a split gurney flap and while I doubt the manufacturer had any aerodynamic intentions it wouldn't be the first time something had unexpected side effects..

[Frank Lee]

I like how you said you got your hands on one...

[aerohead]

That feature has been in the market for 30-years or so.I've never seen anything claimed for the feature and my best guess,is that,the trailing edge of the bra is in accelerated flow and would be sucked into the low pressure there.The spoilers kill the lift and keep things from fluttering and hammering the finish of the vehicle.

[freebeard]

I like that theory.

I dont know if I'm going to fit this yet, I'm not even sure if I'll even get a working car back...

Wut?

...but it strikes me that if this is the case for certain cars, you'd get an aerodynamic benefit as well as protection from road edge gravel and stones helpfully sprayed by uncoordinated cretins...

Possible benefit from acting as a grille block to internal air flow, but some concern about trapping moisture against the paint.

...(although not the head sized rock that was spat out of an artic wheel and almost decapitated my dad (that was one sad looking Mercedes estate)).

I had a fist-sized rock dislodge from the rear duals on a dump truck and strike the hood of my VW Beetle 2ft ahead of the windshield, but it bounced sideways and knocked the rear-view mirror right off the car.