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Old 06-06-2017, 08:09 AM   #1 (permalink)
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Question The Dreaded VG's again...

I have a question over vortex generators. I understand that they have very specific uses, and come with their own drag penalties, but I was wondering if they can be used to reduce certain problem areas of auto aerodynamics.

Looking at their use in Aircraft, they are predominantly used to keep flow attached to a wing with a high angle of attack, to lower stall speed of the wing.

Would it not make sense to install them in front of the front wheel arch/well? By installing one or more VG on the front bumper/wing, would this smooth airflow around the front wheels?

I have no means of testing or simulating this.

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Old 06-06-2017, 08:50 AM   #2 (permalink)
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We did have this thread a while back, see second post on page two.

Most interesting car aerodynamically - 2016

Quote:
The bodywork just ahead of the rear wheel is inset in order to accommodate a series of three vortex generators (3) and still stay within the max width regulations. These VGs are designed to route air around the influence of the rear wheel, shooting the subsequent vorticies into the region of the rear cheese wedge (4) so that the air can be better managed inboard and into the base area of the car.
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Originally Posted by gumby79 View Post
This may be the answer to the difficulty of front wheel skirts..
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Old 06-06-2017, 09:49 AM   #3 (permalink)
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Ah missed that one - thanks.
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Old 06-06-2017, 04:37 PM   #4 (permalink)
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Another tip that most environmentalists will scoff at, is to paint some used engine oil on the area you want to test for use with vortex generators. Then go drive down the highway for a few miles. The wind will leave a oil pattern on the vehicle showing you the air flow pattern. (works like a wind tunnel only with used oil) So you know where to place them, and how to angle them. Plus its easy to retest to get things perfect. I learned this from a friend who races airplanes.

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Old 06-07-2017, 04:19 AM   #5 (permalink)
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Great idea in general - thanks , but as my question was around wheels, I think I'll try to avoid using oil around them...
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Old 06-07-2017, 08:15 AM   #6 (permalink)
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If you go to the link below CFD image showing wheel well air flow disruption.

Pickup Truck Aerodynamics - CFD Study Chevy S10



The front wheels are way worse than the rear wheels as with most vehicles.

I think you are looking at a good problem to solve in other words.
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Last edited by kach22i; 06-07-2017 at 04:12 PM..
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Old 06-07-2017, 10:04 AM   #7 (permalink)
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Are there any general rules of thumb for the size of VGs?

I have also seen on Air craft VG's, they are often angled in a Zig-Zag pattern along the wings, rather than perpendicular to the leading edge. Does anyone know the thinking behind this?
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Old 06-07-2017, 12:51 PM   #8 (permalink)
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What works to replace a front wheel skirt is an air curtain. They are used by BMW and Ford.
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Old 06-07-2017, 02:24 PM   #9 (permalink)
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Latest aero on big trucks is skirting in the front fenderwell following same over the full course. About 1.5" deep. Covers most of air space. See Peterbilt 579 EPIQ aero pics.

That and full length skirting is what my pickup will eventually receive.
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Old 06-07-2017, 03:01 PM   #10 (permalink)
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15 off the direction of flow (not travel) this will require testing before installing.
The top/tip must reach up above the boundary lair into free flow to be able to pull it were you want.
you tube link. Velox Motorsports FRS / BRZ Diffuser Flow Visualization Testing
This will be better than oil , easyer to clean up . They used" China Wight clay "and water.

Zig zag ... my theory is that they are trying to cause counter-rotating vortices. Instead of co-rotating vortices. I dont know witch is better , this may be application specific.

As for use look at the Mitsubishi Evo, top of the back window VG's were used to reduce instability caused from separated air (due to the back glass angle and a trunk too short to allow for reattached boundary lair)
buffetting the back end reducing the safe top speed

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