Lamellar self-blocking grille

[tasdrouille]

You've got a fluid flowing through an opening. As you increase the flow (speed), the opening will only let so much fluid flow through it as the excess will be diverted where there is less pressure. That might give the illusion the grill is "closing up".

[lunarhighway]

from what i gather form posts of people who seem to be more informed on the subject than i am this type of grill would not deliver what it promises...
that's a pitty as the original concept was simple enough and with a relative detailed description so that a copy could be made.

while i can understand smoke streams are easy to misinterpret and some the grill is basically a stack of spoilers; so that could explain the lift reduction, how might they have arrived at the 12% drag reduction figure?...

[TestDrive]

A 12% drag reduction over the drag induced by the earlier prototype grille???

[aerohead]

Originally Posted by cfg83

Hello -

For our purposes, does the scale have to remain the same? Can we have different scales as long as we maintain the same proportions of angle and shape relative to the oncoming air?

Can the shape be simplified to being just a curve? That would make manufacture easy. Just cut up some tubing and install at an angle. I am guessing it *does* need the "fatter bottom", because it looks like an airfoil.

CarloSW2

I was looking at Abbott and Doenhof's airfoil book and I wouldn't want to presume that any change to what Ford wouldn't render a failure.There are so many different airfoils and their performance varies with any change of angle-of-attack,that if I was going to attempt this Lameller grille,I'd follow Ford's proportioning religiously.Without a good windtunnel it would be near impossible to anticipate performance.Maybe CFD.Don't know.Airfoils are extremely labor and time intensive fabrication projects.

[aerohead]

I read everybody's post.It could be,that this grille performed at a 12% drag reduction only on this experimental Ford Capri.In my earlier post,before I got the image online,I mentioned that the production cars which used this "style" of grille,did not realize drag reductions of a scale even remotely close as to that of the experimental car.I can't explain the grilles behavior.It's the only article I've seen which addresses the original inquiry about a self-regulating passive device.All I can intuit,is that these airfoil sections experience a turbulent boundary layer buildup as the car exceeds about 20-mph,and the vorticity associated with this region inhibits passage of air from the stagnation point,spilling over and around the grille.

[metroschultz]

Would you realize the same boundary layer buildup and spillage if you just covered the grill in window screen?

[lunarhighway]

Would you realize the same boundary layer buildup and spillage if you just covered the grill in window screen?

nope, i don't think so...I had the same idea once, but it seems like any mesh will just block the grill with the equivalent of the surface area of the wires, the only effect i could find in literature on the web, was that a mesh tends to smoothen the flow... the airflow will not go turbulent for some distance after the mesh...

perhaps this effect could be beneficial in certain setups, but a mech or screen does not seem to be the magic key...

i've eperimented with the screen , but didn't experiment further after reading info that sugested it wouldn't work, and no real world indications of any "block" effect could be found in my FE results

[cfg83]

Frank -

Originally Posted by Frank Lee

Just teasing. I want to hear what he says about it!

Here is what he has to say :




CarloSW2

.

[aerohead]

Originally Posted by cfg83

Frank -



Here is what he has to say :




CarloSW2

.

Could it be interpreted that Ford of Cologne tested the full-scale Capri development vehicle in their',or someone else's full-scale tunnel,and simply reported the results they discovered?

[cfg83]

aerohead -

Originally Posted by aerohead

Could it be interpreted that Ford of Cologne tested the full-scale Capri development vehicle in their',or someone else's full-scale tunnel,and simply reported the results they discovered?

I think so. At first my Dad said "where's the beef?". What I provided to him did not explicitly state that wind tunnel testing was conducted. After we talked, he said that they probably *did* do wind tunnel testing because they *should* have had the facilities to do it. What's really needed is the original academic paper that documented everything. He agreed with another poster that it is hard to tell how accurate the drawing is to the grill as described. It could just be an "artist's rendering" for a magazine that leaves a (devilish) detail out.

I asked and he said you could simplify it to being "just flat slats", but he would not expect it to perform as well.

CarloSW2