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Old 11-13-2007, 12:27 AM   #11
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Hello -

Ok, I found the document, so it was part of the conference :

SAE Technical Papers
Title: Improving Automotive Fuel Efficiency with Deturbulator Tape
Document Number: 2007-01-3458
http://www.sae.org/technical/papers/2007-01-3458

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Old 11-13-2007, 01:46 AM   #12
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Quote:
Originally Posted by 8307c4 View Post
Just use duct tape, what's the difference?
Hunting around a little:

Seems to be that traditional glider turbulator tapes are raised vinyl sawtooth tape -- with different lengths/frequencies of the sawtooth pattern.

Sinha's turbulator tape looks to be more like a sandwich -- imagine duct tape with a thin plastic set of stand-offs.

1) Bottom layer's the adhesive portion to stick it to the vehicle / airfoil surface.

2) Then there's the "ridged substrate", a set of (equally spaced) standoffs above the adhesive layer.

3) Atop the ridges is a thin membrane -- probably made of mylar, or since the examples are sort of shiny... aluminum backed mylar?

The height of the tape, top to bottom, according to the diagrams he's used in his SAE presentations, is only 50 to 100 micrometres (2 to 4 thousandths of an inch). Erm, I don't think it's much thicker than duct tape would be, really. Sounds a lot more like coroplast scaled down, with saran-wrap on top instead of the hard plastic sheet the one side.

Instead of presenting a "rough" surface, like the sawtooth tapes, or say, sandpaper grit-side-up, the design Sinha's testing seems to vibrate the membrane on top to perturb airflow and/or dampen and remove energy from turbulant flows to make them more calm and laminar, instead of strong, rolling eddies.
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Old 11-13-2007, 02:23 AM   #13
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after a brief look trought the first document cfg83 posted one thing struck me.
i've been wondering for a while if the windshield to roof transition is't an area that could use more attentiom, and this seems to confirm it somewhat. afterall what good it it to worry about attachement of airflow at the end of the car if it aleady gets detatched at the beginning of the roof. so these turbulators or even vortex generators might work there.
i wich i had a moonroof, that would make tuft testing quite easy.
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Old 11-13-2007, 02:39 AM   #14
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Hello -

Here's a pic from the report to illustrate ChrstphrR's commentary :

http://www.sinhatech.com/SAE-APAC-20...08-06-2007.pdf
Attachment 1072

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Old 11-13-2007, 02:42 AM   #15
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lunarhighway -

Quote:
Originally Posted by lunarhighway View Post
after a brief look trought the first document cfg83 posted one thing struck me.
i've been wondering for a while if the windshield to roof transition is't an area that could use more attentiom, and this seems to confirm it somewhat. afterall what good it it to worry about attachement of airflow at the end of the car if it aleady gets detatched at the beginning of the roof. so these turbulators or even vortex generators might work there.
i wich i had a moonroof, that would make tuft testing quite easy.
I was thinking of using the AirTabs (http://www.gassavers.org/showthread.php?t=5392) to make the air "jump over" the windshield wipers, but maybe they would work in the same location as the Deturbulator Tape?!?!?

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Old 11-13-2007, 03:20 AM   #16
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Quote:
I was thinking of using the AirTabs (http://www.gassavers.org/showthread.php?t=5392) to make the air "jump over" the windshield wipers, but maybe they would work in the same location as the Deturbulator Tape?!?!?
i remember an autospeed article where they made a full fairing on a first gen prius to cut down wiper noise. it worked for doing that, but no real FE fains where reported as far as i recall. there's a high pressure area that shields the wipers anyway and forms a virtual fairing that smootens out the hood to windshield transition. on the other hand if a similar turbulent bubble would sit on the rooftop that would add frontal area + dragg. so that's where i'd place my AirTabs if i had them.

than again my aerodynamic understanding is rather inclompete so i might be wrong about this
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Old 11-13-2007, 02:11 PM   #17
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Hello -

What I find interesting is that instead of the form of the car being "static" in relation to the air resistance, it is instead interacting with the airflow and modifying the turbulence dynamically. If this was designed for airplanes that normally operate at air speed X, would a different version for cars (aka modifying the dimensions of the elements of the tape) work better for cars driving at highways speeds around 65 MPH? Orrrrrrrrrrr, because the membrane is acting dynamically, maybe it operates over a range of speed? Also, gliders are going closer to car speeds, right?!?!?!?

... time passes ...

Answering my own question with this picture :

http://www.sinhatech.com/SAE-APAC-20...08-06-2007.pdf - Page 12
Attachment 1074

From the above, it seems that the glider's airspeed is comparable with cars. I highlighted 51.8 MPH as the "sweet spot", at least based on the above test. On the ground this sweet spot would change (right?!?!?!).

If it did need to be modified, then I think it would need to be modified for even greater top speeds (I was originally thinking the opposite).

Knots to MPH conversion references :

Convert Knots to Miles Per Hour
http://www.flightsimaviation.com/rul..._per_Hour.html

Conversion table for knots to miles per hour
http://www.flightsimaviation.com/rul..._per_Hour.html

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Old 11-13-2007, 02:33 PM   #18
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Quote:
Originally Posted by 8307c4 View Post
Just use duct tape, what's the difference?
I've got plenty of duck tape on my car but I'm not going to place any on a surface that is already a smooth curved surface, but to deflect air from going under the car and into the wheel wells.
Looks like yet another gimmick to me.
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Old 11-13-2007, 05:48 PM   #19
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Question

In the photo of the Escalade model in the wind tunnel (click on the photo for a larger image) we can see the deturbulator strip across the front of the roof just aft of the windshield. Do you think the tape going across the hood to secure the model has any measureable effect on the aero?

We've seen photos of vortex generators on the sides of vehicles; might deturbulator strips be beneficial there, too? If so, where on the sides do you think would be most effective?
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Old 11-16-2007, 02:43 PM   #20
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If I understand right, these tapes are ridged to vibrate with the wind pressure...

I suggest sport tape for experiments: It is fabric, very cheap and comes off easily. Duct tape is just slick. I don't have time for these experiments, as I will first pursue other options.
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