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Author Topic: Vortex Generators:  (Read 19443 times)

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Offline ggl205

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Re: Vortex Generators:
« Reply #30 on: August 24, 2018, 08:47:47 AM »
OK, now it is clearer. VG's have to angle in on one another for them to be effective (see image). I have seen some VG's that look like raised NACA ducts that I guess work the same way so long as you mount them with the bigger end pointed at airflow.

John

Offline malibuguy79

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Re: Vortex Generators:
« Reply #31 on: August 26, 2018, 07:40:45 AM »
The ones that I put on my car had a template that makes them gradually angle out from center.  Progessing from 0 to 15 degress irrc (this was like 8 years ago)
-Greg...the exhaust guy

Offline tauruck

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Re: Vortex Generators:
« Reply #32 on: September 05, 2018, 05:41:56 PM »
Prof. Joseph Katz recommended I use them on the truck I was building????.

Offline SPARKY

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Re: Vortex Generators:
« Reply #33 on: September 06, 2018, 12:58:25 PM »
where  :?
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Offline 4-barrel Mike

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Re: Vortex Generators:
« Reply #34 on: September 06, 2018, 01:42:17 PM »
Mike Kelly - PROUD owner of the V4F that powered the #1931 VGC to a 82.803 mph record in 2008!

Offline tauruck

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Re: Vortex Generators:
« Reply #35 on: September 06, 2018, 04:00:42 PM »
The Ranchero I was building. Joe suggested putting Polycarbonate panels on the sides between the rear part of the roof and load box cover.
I wanted to keep the thing looking like I built it so he said Vortex generators would help to a degree.

You guys may not remember but Joe Katz's students built a quarter scale model of my truck at SDSU on their 3 axis milling machine
and wind tunnel tested it. I've still got all the photos and aero results from San Diego. The truck had a CD the same as a Porsche GT3.

The iffy area was between the rear window andload box.

Offline ggl205

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Re: Vortex Generators:
« Reply #36 on: September 06, 2018, 04:46:19 PM »
Prof. Joseph Katz recommended I use them on the truck I was building????.

Joseph Katz book on race car aero was one of the first I read. Packed with great aero information.

John

Offline tauruck

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Re: Vortex Generators:
« Reply #37 on: September 26, 2018, 11:26:23 AM »
I wish I could see Joe's car collection. He said he had a few. :wink:
A genuine guy and always helped and answered my emails.

What he did for me was unbelievable. 8-)

Offline rockracer

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Re: Vortex Generators:
« Reply #38 on: August 14, 2020, 01:56:07 PM »
I was thinking of putting these on my roof rack wind deflector to help break up the wind going over/to the trailer.

Thought I'd check in here first to see what you all thought of these.

Do they really help with the suction coming off the back of the trailer ?

Offline maj

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Re: Vortex Generators:
« Reply #39 on: August 14, 2020, 06:15:43 PM »
They need to be in clean (laminar)air to work, any turbulence there any you may as well forget it
I brought some to try and improve handling on an APS streamlined bike , but it seems my problems were bigger than the help these gave ;)

Offline Bratfink

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Re: Vortex Generators:
« Reply #40 on: August 15, 2020, 09:09:28 AM »
The truck had a CD the same as a Porsche GT3.

Porsche GT3 doesn?t have a Cd you?d want for an LSR car... big dangly wings and massive open cooling. There?s at least 20 if not 25 counts (1 count is 0.001 Cd) of cooling drag on that car.

The thing I?m starting to notice is that not many people in the community know what they should be targeting for drag, lift or frontal area.

In the production industry we build databases of competitive products so we can try to predict trends etc.

If you guys are interested and want to share data I can put together something like that for each of the classes (that generate this sort of data). We?d have to account for differences in testing methodology but I think I might be able to do it with an uncertainty band.

Let me know if there?s interest, the more people on board the better the data will be. My intention would be to publish all of this for the community, may even be an SAE paper in it.

Offline rockracer

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Re: Vortex Generators:
« Reply #41 on: August 18, 2020, 10:09:25 PM »
They need to be in clean (laminar)air to work, any turbulence there any you may as well forget it

My roof rack is almost a foot back from the top of the windshield . I made the wind deflector (flat plastic) the same angle as the windshield. Which helped a lot.

So would my roof rack be considered in laminar air OR would the air going over the windshield be turbulent  ?

I may order only 10 ($30) just to see if any......

My bug line on the trailer is the last 4" at the top.
It used to be lower , so improvements have helped.

Offline Rex Schimmer

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Re: Vortex Generators:
« Reply #42 on: August 19, 2020, 12:58:07 PM »
Vortex generators will work in turbulent air but it has to be "attached". All air flow past the point of the critical Reynolds number is turbulent but if the surface is smooth the air flow can remain attached. Although attached laminar air flow has much lower drag than attached turbulent flow, once the air flow becomes turbulent and unattached the drag is radically increased.  There are a number of long cars with flat sides that have an abrupt transition to the cone of the tail section, which would be a perfect place for vortex generators, they may not be effective simply because the turbulent boundary layer is to thick.

Rex
Rex

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