Texas Tech Study "Wing" Details

[Kardell]

Does anyone know if the "wing" mod, as accomplished by Texas Tech in their 1988 wind tunnel study, include side closeouts/sails? Or was the mod just an extension of the horizontal roofline (for X inches at Y degrees divergence)? I can visualize the aerodynamic function of aft cab extensions/sails. But it might be really convenient to omit them for a "practical" truck application. TIA.

Matt

[kach22i]

Is this regarding Pick-Up trucks?

[Kardell]

Yes. Phil Knox has posted some of the results on here. But I'm not clear regarding the need for side "sails" to tie into the roof "wing". (I don't have a copy of the report)

[aerohead]

Originally Posted by Kardell

Yes. Phil Knox has posted some of the results on here. But I'm not clear regarding the need for side "sails" to tie into the roof "wing". (I don't have a copy of the report)

Tech attached the wings to the cab.When Gilkison did the T-100,he was squeamish about drilling into the sheet metal,and ended up fabricating the 'wing' in conjunction with the tapered sail panels,which just slipped into the existing stake holes of the rails.The sails had plex windows to kill the blind spot created by the sails.
It was just a quick and dirty proof of concept.

[kach22i]

If I recall correctly, those roof wings were not true wings in that there was no flow under them, being sealed along the leading edge to the roof, more like roof spoilers they were.

Canted down a few degrees they induced quite a bit of lift.

The roof wing I made contributes to down force (see link in signature below).

The leading edge is beveled allowing an air slot or small opening at the leading edge.

The air in this slot I believe is accelerated by the narrowing, thereby lowering it's atmospheric pressure, and the higher pressure above the wing is drawn downward to fill the void left.

This then flows along the bed cover, where it meets the rear spoiler.

Not until this flow hits the spoiler is down-force realized.

At least this is my current theory.

The winglets on the Texas Tech roof spoilers delay vortexes from forming. Vortexes form at the intersection of side and roof because the air tends to follow a longer path along the roof and is at a different (lower) pressure than the side air. Once the flows meet and move into each other, they start to swirl, hence vortex formation and drag.

[aerohead]

Originally Posted by kach22i

If I recall correctly, those roof wings were not true wings in that there was no flow under them, being sealed along the leading edge to the roof, more like roof spoilers they were.

Canted down a few degrees they induced quite a bit of lift.

The roof wing I made contributes to down force (see link in signature below).

The leading edge is beveled allowing an air slot or small opening at the leading edge.

The air in this slot I believe is accelerated by the narrowing, thereby lowering it's atmospheric pressure, and the higher pressure above the wing is drawn downward to fill the void left.

This then flows along the bed cover, where it meets the rear spoiler.

Not until this flow hits the spoiler is down-force realized.

At least this is my current theory.

The winglets on the Texas Tech roof spoilers delay vortexes from forming. Vortexes form at the intersection of side and roof because the air tends to follow a longer path along the roof and is at a different (lower) pressure than the side air. Once the flows meet and move into each other, they start to swirl, hence vortex formation and drag.

I suppose Tech could have fished around for a different term.
The premise of what they were after was to tailor the locked vortex behind the cab.
The 'wing' was active underneath in the sense that the vortex was licking the rear face of the cab as it ascended towards the roof,then circulating aft,after being captured and redirected by the underside face of the cantilevered projection.
The low pressure of the tornado,spinning above the bed was communicated under the half-tonneau to the inner face of the tailgate;creating a beneficial pressure differential across the gate,which,along with flow reattachment atop the tonneau,created the 17% drag reduction.
Lift was cut substantially with the air crashing down onto the tonneau.

[kach22i]

Originally Posted by aerohead

The low pressure of the tornado,spinning above the bed was communicated under the half-tonneau to the inner face of the tailgate;creating a beneficial pressure differential across the gate,which,along with flow reattachment atop the tonneau,created the 17% drag reduction.

Lift was cut substantially with the air crashing down onto the tonneau.

RE: Lift was cut substantially

This finding might be in a different or more recent version of the report than I have read before.

Could someone please post a link to the PDF in question?

A half a dozen posts talking about a paper not even linked to is starting to look a little silly - just my opinion.

[Kardell]

Phil: Thanks for your reply.

Summarizing: The test data and your fluidynamic description imply that side "sails" are NOT required to achieve the drag reduction with the "wing" and the 1/2 cover.

Kach22: I have not come across a PDF of the paper on the web. AIAA will sell you a copy, but that also probably means it's copy-right protected and shouldn't be posted to the web.

[aerohead]

Originally Posted by kach22i

RE: Lift was cut substantially

This finding might be in a different or more recent version of the report than I have read before.

Could someone please post a link to the PDF in question?

A half a dozen posts talking about a paper not even linked to is starting to look a little silly - just my opinion.

From the source:SAE Paper # 881874,in the section on CONCLUSIONS,page 10,paragraph-4,"An interesting and unexpected discovery in the scale model testing was the 15% to 30% decrease in aerodynamic lift measured for the wing and bed cover combination.This decrease in lift will improve vehicle handling at highway speeds."

[kach22i]

A:

Originally Posted by Kardell
.....fluidynamic description ...."wing" and the 1/2 cover

B:

Originally Posted by aerohead

....scale model testing....... wing and bed cover combination.

Correct me if I'm wrong, but it looks like we have two means and methods with the same end result.

A: computer model (fluidynamic description) and 1/2 bed cover (aft half, right?).

B: scale mode and full bed cover.

Like I mentioned, older/earlier reports recorded a great increase in lift. I can only assume that there must have been some slight but important changes to the roof wing/spoiler for the results to have turned around so.

I bet (one dollar) based on my own experiences, that the roof garnish now has an air-gap between it's leading edge and the cabin roof.

EDIT-1:

Feysal Ahmed Adem
B.S., Addis Ababa University, Ethiopia, 1999
http://ecomodder.com/forum/showthrea...1-a-19525.html

Originally Posted by kach22i

Did some more research. Pages 55-58, the conclusion on "rear roof garnish" is not exactly what I had in mind. Their "garnish" is set at a 12 degree downward angle, and I'm guessing about 6 inches deep.

PDF link:
http://csus-dspace.calstate.edu/xmlu...pdf?sequence=1

This is not one of the Texas Tech papers, apologies to anyone I may have mislead.

I should note that the roof garnish has been reported to be 24"-32" not 6" deep.