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Author Topic: Vortex Generators:  (Read 3698 times)
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Rex Schimmer
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« on: December 11, 2016, 03:10:44 PM »

Excellent paper by some engineers at Mitsubishi Motors on the sizing and application of Vortex Generators (VG) to reduce drag. Very applicable to Bonneville cars. I can think of several streamliners and lakesters that could use this technology.

http://www.4g63.de/facts/vortexgenerator-evo-mitsu.pdf

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« Reply #1 on: December 11, 2016, 04:23:16 PM »

Several are.
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« Reply #2 on: December 11, 2016, 07:27:06 PM »

Where they are allowed I hope!!!!
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« Reply #3 on: December 11, 2016, 08:59:28 PM »

In 1991 the Herbert Steen liner had them on the back to help the air transition to solve a chute deployment issue. There was a lot of people asking "what the hell are those things?".
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« Reply #4 on: December 11, 2016, 10:17:39 PM »

A few streamliners & a few others run 'em


* Picture updates 665.jpg (29.18 KB, 406x330 - viewed 175 times.)

* 13716130_566574826855922_7778993990963611696_n.jpg (76.63 KB, 950x712 - viewed 169 times.)
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« Reply #5 on: December 11, 2016, 10:46:54 PM »

I could be completely wrong... but the posted paper has the delta turned the other way (180 degree rotation) than the pictures that are posted. ??
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Seldom Seen Slim
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« Reply #6 on: December 12, 2016, 08:11:39 AM »

The Nish family has used and promoted the generators for years.  Have 'em on the van, the race cars (as allowed, I presume) and so on.  I'd say they'd be a reasonable source for information - maybe even data.

I wonder if Layne and Tom*, at Darko wind tunnel, have ever tried to quantify the things?

*Or anyone at any wind tunnel, or even you, Woody.
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Jon E. Wennerberg
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« Reply #7 on: December 12, 2016, 08:22:06 AM »

Putting vortex generators at the trailing edge of a surface, as shown in the above photos, is pointless.   
To be functional they need to be in a region where the flow has not already detached, and their purpose is to enhance attachment to the downstream surface.  In the photos, they are probably in a region of detached flow and there is essentially no downstream surface.  Wrong on both accounts.
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« Reply #8 on: December 12, 2016, 08:33:54 AM »

Putting vortex generators at the trailing edge of a surface, as shown in the above photos, is pointless.  
To be functional they need to be in a region where the flow has not already detached, and their purpose is to enhance attachment to the downstream surface.  In the photos, they are probably in a region of detached flow and there is essentially no downstream surface.  Wrong on both accounts.


IO is correct. Look at the aviation industries use of VG. They are almost always before the recovery area of the foil. Their intended use is to promote attachment of the flow in areas of separation. Having no place to reattach the air means they are simply creating drag or aiding in moving the CP aft.

They also do cause separation drag in the upper areas of their outflows. One of the other benefits of VGs in aircraft is that the air behind them can become "excited" which provided more energy for lift. That energy is in the form of vortexes (hence the name - Vortex Generators) which is not laminar flow. The use of VG in aircraft can lower the stall speed of a wing as well as increase the lift so they do serve a purpose.

You never see the use of VG in production aircraft. VG are typically applied in the post-production phase of the aircraft and usually to adjust characteristics or tune a poor design shape. Most modern aircraft do not come with them from the factory and not all aircraft are certified for their use. If they were the utopia that were sold to the aviation industry in the late 80's and early 90's you would see them employed more widespread.

On cars, they have their use but like IO stated if there isn't anyplace for air to reattach to their employment provides limited benefit.

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« Reply #9 on: December 12, 2016, 11:39:15 AM »

Putting vortex generators at the trailing edge of a surface, as shown in the above photos, is pointless.   
To be functional they need to be in a region where the flow has not already detached, and their purpose is to enhance attachment to the downstream surface.  In the photos, they are probably in a region of detached flow and there is essentially no downstream surface.  Wrong on both accounts.


They may not reattach the airflow at the end of the vehicle, but perhaps numerous small vortexes have less drag than one big one. I could see them working like the trailer tails on semi trucks.
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« Reply #10 on: December 12, 2016, 12:23:00 PM »

They may not reattach the airflow at the end of the vehicle, but perhaps numerous small vortexes have less drag than one big one.
As long as we're talking perhapses, the benefit in preventing the big vortices could be stability. Them big 'uns can grow slowly, collapse suddenly, and are asymmetrical.
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« Reply #11 on: December 12, 2016, 01:54:20 PM »

Putting vortex generators at the trailing edge of a surface, as shown in the above photos, is pointless.   
To be functional they need to be in a region where the flow has not already detached, and their purpose is to enhance attachment to the downstream surface.  In the photos, they are probably in a region of detached flow and there is essentially no downstream surface.  Wrong on both accounts.


They may not reattach the airflow at the end of the vehicle, but perhaps numerous small vortexes have less drag than one big one. I could see them working like the trailer tails on semi trucks.

Having been involved in transportation and logistics for over 30 years I'll provide a simple observation. If you don't see the likes of Schneider, JB Hunt, UPS, FedEx, Ryder... adopting it onto their fleet vehicles there is a reason. I've been part of many a study on how to make tractor/trailer combos more efficient. After payroll, fuel is the number one expense. Anything you can do to cut it even by single digit percentages is adopted immediately by these organizations.

A simple cost benefit analysis done by these organizations will tell them if it is worth it or not. These guys aren't looking to go faster, they are looking for more fuel efficient. Coincidentally, MPG vs MPH have a common thread - aerodynamics. Trust me, these large carriers have annual fuel spends in the hundreds of millions of dollars. If they could save 1% with the bolt-on devices they would outfit their fleets overnight.

Always look at the big carriers and what they adopt, the little guys or the one-off guys are easily swayed...I've seen it a hundred times.
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« Reply #12 on: December 12, 2016, 03:31:25 PM »

Back in the mid 90s I postulated the skirts we now see on trailers.  Dang it, shoulda patented the idea.  But as for aero fuel savings -- on our straight trucks I spec'd Noze Cones over the objection of the dealer.  Gee, I wonder why my fleet always got distinctly better gas mileage. . .

As for trailer tails -=- more and more of 'em out there, and yes, on the bigger fleets.  Schneider doesn't yet -- but they've got faux moon discs on the drive wheels of the tractors.  We drove back and forth to Indy this past week and saw dozens of tails deployed.  Maybe it's a smaller percentage improvement and takes a big enough company to commit.  Crete has some, Willis has lots, Covenant many.  Over to you and back to racing aero...if you want.
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Jon E. Wennerberg
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« Reply #13 on: December 12, 2016, 07:27:16 PM »

Hmmm??  I know that my neighbor, Toyota, has place several VGs on their new Prius near the rear of the vehicle.  Several are integrated in the tail lights and several are underneath right before the rear bumper.
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« Reply #14 on: December 12, 2016, 07:52:31 PM »

Hmmm??  I know that my neighbor, Toyota, has place several VGs on their new Prius near the rear of the vehicle.  Several are integrated in the tail lights and several are underneath right before the rear bumper.

Might have more to do  with keeping the lights and body clean from accumulation of road dirt.  At one time Mercedes made a reasonably big deal out of how the ribbed shapes on their tail lights tended to keep them cleaner than otherwise.  (Didnít make them easier to wash, though.)
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