Need advice on NACA duct placement to airflow on curved surface.

[JulianEdgar]

Originally Posted by freebeard

You find yourself down here in the mud with the rest of us?

I agree with aerohead. I've seen some shallow boxed cavities.



If you can't trust Gaylard, who can you trust? My favorite example would be the Cobra Coupe.

Don't you mean you agree with me?

And as far as I know, Dr Gaylard had nothing to do with the diagram you cite.

[freebeard]

It's possible for me to be wrong twice in one post.

I was agreeing that perforation would be counterproductive. I though you took the opposite stance.

The screen grab was from Coventry and Jaguar so I ass-umed, is he with Warwick?

[aerohead]

Originally Posted by JulianEdgar

Sure



Only if you think that's how box cavities work. I don't think that - because they reduce drag even when the extensions are not angled inwards and so when there's no reduction in cross-sectional area.

It's the old thing - to a hammer everything looks like a nail. Or, once you have a theory in your mind, you want to apply it to everything.

Very true! As with Hucho's example behind the VW Transporter.( another example from Hucho, is the elongated rectangular 'lozenge', resembling an Airstream trailer body, which hit minimum drag at a particular length.
What would be instructive, would be a side-by-side comparison, one with, and one without the angles.
Alan J. Bilanin's box-cavity, US PATENT # 4,682,808, filed, July 24, 1985, incorporated three captured-vortices in his ( top and both sides ), within rearward's facing 'steps'.

[freebeard]

Only if you think that's how box cavities work. I don't think that - because they reduce drag even when the extensions are not angled inwards and so when there's no reduction in cross-sectional area.

All this thinking when one could be out testing.

I thought that angled, stepped and curved extensions were pretty much equivalent for a given reduction in cross section.

Can anyone help? I am unable to find the [yellow] side view of Morelli's Urban Car that had it's maximum cross section at the C-pillar, with a 45% chamfer.

It speaks to my understanding before Ecomodder.

I have a big scrap of aluminum sheet and a Geo Metro. I'd be interested in an annular half-ring that clips onto the rear hatch. Suggested profile? Chamfer? Tearing edge?

[Vman455]

Originally Posted by Vman455

Well, shoot--I have a couple papers, but they're both too big to upload here. I'll see if I can figure something else out.

I still don't have anywhere to host these, and it looks like they aren't available online. This is one of them, but full-text isn't available for some reason.

[AeroMcAeroFace]

I was going to read this but got distracted by fred hamlin, I don't know fred hamlin but I don't think that is his picture.

[freebeard]

If it is then he is very unfortunate.

[aerohead]

Originally Posted by freebeard

All this thinking when one could be out testing.

I thought that angled, stepped and curved extensions were pretty much equivalent for a given reduction in cross section.

Can anyone help? I am unable to find the [yellow] side view of Morelli's Urban Car that had it's maximum cross section at the C-pillar, with a 45% chamfer.

It speaks to my understanding before Ecomodder.

I have a big scrap of aluminum sheet and a Geo Metro. I'd be interested in an annular half-ring that clips onto the rear hatch. Suggested profile? Chamfer? Tearing edge?

Wasn't that the 'ring-vortex' and turbine-wheel study that he published about?

[freebeard]

Found it. Via a search on "all forebody" which returned an odd print version of the page.

https://ecomodder.com/forum/showthre...283-print.html



It's from your album. Now why did I cite it? Oh, yeah, 45° chamfer.

edit:
It represents my thinking before I came to Ecomodder, a bullet shape.

[Cd]

Unless there is a change of plan, I plan to tuft test my car tomorrow with the NACA ducts.
I'm at my parents' and will be having them as a chase vehicle ( So expect the video to be quick, and probably not that useful )

I plan to have them video the car from directly behind, then from the side.
Time permitting ( I'm here for a wedding ), I would then pull over and tape over the NACA ducts and they would again video the car from behind.
I'd like to ask what areas on the car that you all would like to see on video in the test.
By the way, I also have a fin installed on one side