Lamellar self-blocking grille

[elhigh]

Originally Posted by Big Dave

Looks like a good idea but it is probably beyond the capability of any DIYer.

You'd have to get the airfoil shape, pitch and spacing JUST RIGHT for it to work worth a hoot.

You could guess, I suppose, but what good is a design based on a WAG?

For those of us with block-o-cheese front ends - looking at you, Dave, and myself for that matter - it shouldn't be that big a deal - no need for complex curves.

Where'd I leave that set of castoff venetian blinds...?

And hey - what the heck is a WAG?

[aerohead]

Originally Posted by cfg83

Hello -

Could this be an example of a "combo grill"? :

Help with my aero mods: 1.8L 05 Auto Toyota Corolla


The shape looks close to the description, but each slat is honeycombed with smaller holes. Maybe the smaller holes "vanish" at higher speeds?!?!?! Probably just more designer poop.

CarloSW2

If Santa would bring ecomodder a big wind tunnel,we'd be able to check this sort of thing out.

[Frank Lee]

I bet it could be done with yarn.

[cfg83]

Frank -

Originally Posted by Frank Lee

I bet it could be done with yarn.

Yeah, but the wind tunnel would be so much cooler. When I went to UCLA in 1984, for years I would pass by this big rusty cylindrical tank laying on it's side, maybe half the size of a gas truck tank. One day when my Dad was visiting, he told me that it was the wind tunnel they built for *him* and other students as part of their research in the 1950's/1960's. Those were they daze!

Back on topic, wouldn't a pressure gauge behind the grill get the job done?

EDIT: Wouldn't it be easy to model this grill in a CFD program? You don't have to model the whole car, just the grill, the radiator, and some hood/side parts of the car.

CarloSW2

[cmroseberry]

I maintain my assertion that there is nothing special about the grille from the PopSci article. Any internal cooling flow passage that presents some net flow resistance will result in an increasingly greater portion of the external flow going outside rather than inside the passage as the vehicle speed increases. Although, the capture streamtube for the cooling passage gets increasingly narrow with vehicle speed, the volume of flow through the cooling passage still increases because the pressure difference between the inlet and outlet increases with vehicle speed. (The above discussion is a slight simplification: it is actually the ratio of external and internal velocities that determines the pressure loss coefficient and the streamtube shape.)
I researched automotive cooling airflows from 1988 to 1990 and co-wrote an SAE paper on my findings. If there actually were some amazing aerodynamic trick with a front grille, Jack Williams, my co-author from Ford, surely would have been aware of it. Jack Williams now teaches short courses for SAE on vehicle cooling aerodynamics. Anyone who wants to learn the state-of-the-art for vehicle cooling performance and drag should go to sae.org and buy a couple of Jack’s latest papers. 2001-01-0996 “Aerodynamic Drag of Engine-Cooling Airflow with External Interference” and 2002-01-0256 “Cooling Inlet Aerodynamic Performance and System Resistance”.

[Frank Lee]

I believe you.

It's just the fact that they are doing this "speed based restriction" in an attempt to regulate flow rather than just sticking an eggcrate grille on there.

[Sandy]

Originally Posted by elhigh

And hey - what the heck is a WAG?

Wild A** Guess.

as opposed to a SWAG
which is a
Scientific Wild A** Guess

[Eighty-Nine Si]

I suspect a similar effect could be achieved with holes of the proper diameter and spacing. Titrating-up would facilitate testing. Hmmm.

[Frank Lee]

You are correct; screens are known to behave like that.