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-   -   Vortex generators in diffusers (https://ecomodder.com/forum/showthread.php/vortex-generators-diffusers-37511.html)

fastflyer 05-19-2019 08:24 AM

Vortex generators in diffusers
 
Hi, has anyone tried the Vortex generators or airtabs as if they were a diffuser?

In theory, they should push the air upwards, enhancing the effect of the diffuser, not?

freebeard 05-19-2019 05:46 PM

Yes, but...

Quote:

How The New Ferrari FXX-K Evo Can Make Over 1,800 Pounds Of ...
https://jalopnik.com/how-ferraris-ne...800-1819951838
How The New Ferrari FXX-K Evo Can Make Over 1,800 Pounds Of Downforce. ... Ferrari added vortex generators on the belly pan, which "capitalised on the accelerations created by the rear system ...
Quote:

Devon GTX. Supercar made in USA - Autoblog.gr
https://www.autoblog.gr/2009/08/19/d...r-made-in-usa/
The team's efforts led to the incorporation of a three-piece belly pan constructed of carbon fiber. In addition to providing enhanced under-car surface appeal and aerodynamics, the belly pan carries revolutionary "vortex generators" for improved downforce - a key enabler to the vehicle's exceptional agility and balance.
I can't find the picture[s] I've seen of the underside of a modern race car, but vortex generators generally are used to add energy to the flow to encourage reattachment to the body. The race cars (I saw) use them behind the front wheels at the beginning of underfloor tunnels. On a diffuser they'd be at the front of it, but given the nature of the airflow in the plenum between the underbody and the ground, fences are what are used, to segregate and straighten the flow.

kach22i 05-19-2019 07:02 PM

Maybe not what you were asking for, but something said reminded me of this image below from page-2 of the link.

Most interesting car aerodynamically - 2016
https://ecomodder.com/forum/showthre...6-a-34854.html
http://www.mulsannescorner.com/AudiR...st2016-SC3.JPG

Original source:
Mulsanne's Corner: Race Car Engineering Le Mans 2016
http://www.mulsannescorner.com/Kolle...ce2016-SC1.JPG
http://www.mulsannescorner.com/Toyot...ne2016-SC1.JPG

woodstock74 05-20-2019 11:03 AM

Quote:

Originally Posted by kach22i (Post 598512)
Maybe not what you were asking for, but something said reminded me of this image below from page-2 of the link.

Most interesting car aerodynamically - 2016
https://ecomodder.com/forum/showthre...6-a-34854.html
http://www.mulsannescorner.com/AudiR...st2016-SC3.JPG

Original source:
Mulsanne's Corner: Race Car Engineering Le Mans 2016
http://www.mulsannescorner.com/Kolle...ce2016-SC1.JPG
http://www.mulsannescorner.com/Toyot...ne2016-SC1.JPG


Might as well out myself...that site looks familiar :)

fastflyer 05-20-2019 03:27 PM

Has anyone tried something like this?

https://www.sigmaautomotive.com/perf...kz/image12.jpg

Site: sigmaautomotive

kach22i 05-20-2019 04:05 PM

Quote:

Originally Posted by fastflyer (Post 598561)
Has anyone tried something like this?

That's what I was looking for evidence of in that race car but could not find.

No, I have not seen that done before.

Is there any point to putting those at the very end when there is nothing to reattach to?

There is just a wake behind the car.

And in this white car's situation, not even a plane before it, just some very confused air.

From the clip flanges there seems to be a belly pan piece missing.

fastflyer 05-20-2019 04:22 PM

I think it can improve because it can make the air move up where there is less pressure and thus gain more downforce. And reduce wake area.

The same happens with the airtabs installed on the sides of the trailers.

And how race cars have diffusers, they should not need this.

freebeard 05-20-2019 05:59 PM

Quote:

Has anyone tried something like this?
The picture suggests but doesn't prove that someone has.
vs
Those aren't vortex generators, those are (wimpy) fences.

Vman455 05-20-2019 09:28 PM

Quote:

Originally Posted by freebeard (Post 598574)
Those aren't vortex generators, those are (wimpy) fences.

It looks like they're all pointing straight back, aligned with the car's direction of travel. But for those to generate vortices, they need to present surface area to the flow i.e. be placed at an angle to the flow. So, depending on what the flow field looks like back there, they may or may not be vortex generators.

But, I have several questions:
1) Does generating a vortex or several vortices there mean they'll migrate upward, against gravity?
2) What effect or interaction will that vortex/those vortices have on the large vortices formed naturally and shed by the car's C-pillar?
3) How many times can one say "vortices" before it starts to sound weird?

freebeard 05-21-2019 12:42 AM

It's hard to tell from that angle but it looks like the two sides are set at a slight angle. Just not enough— compare to the V-shaped Airtabs.

I don't think anything can act at right angles to the airflow. Any effect will propagate downstream.

If you want to wrap air around an edge, you need the Coanda effect.

https://ecomodder.com/forum/member-f...70-imagesa.jpg

Else, cold plasma actuators. Both require energy.


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