Vortex generators under your racecar question

[Iceracer33]

let's say you have a street legal racecar, flat front splitter with undertray going back to front tire stock undercarriage with crooked exhaust and couplings and then a badass rear difuser from the rear tire to the bumper. Let's keep this about "under the car" question. Vortex generators do some really neat things with the air including changing air direction, creating a small low pressure area and so on.

So, how could you make best use of vg's to maximize downforce without caring too much about drag?
Would you:

1. Put them at the end of the front tray to create a small low pressure area to help suck some air from the motor compartment and also help the air for the rear diffuser?
2. Put them at the leading edge of the front splitter To help the front splitter work better?
3. Put them at the leading edge of the rear diffuser to help the air stay attached?
4. Or even some in front and rear going in the same direction to help the vortex's grow bigger?
5. Don't add any?

Just throwing some things out to see if anybody has had experience with any of these options, this is truly just a fun question but if you think it may be beneficial to maximize downforce using them I may even try it out.

 

[jack action]

Vortex generators do some really neat things with the air including changing air direction, creating a small low pressure area and so on.

That is not what vortex generators do:

Vortex generators are most often used to delay flow separation.

You have to install them where flow separation may occurs:

To accomplish this they are often placed on the external surfaces of vehicles and wind turbine blades. On both aircraft and wind turbine blades they are usually installed quite close to the leading edge of the aerofoil in order to maintain steady airflow over the control surfaces at the trailing edge.

On a car, the place where it should be the most effective is probably on the top, near the windshield, or on the front of the hood.

I don't think putting them anywhere else could make a (positive) difference.

So, how could you make best use of vg's to maximize downforce without caring too much about drag?

If they work as intended (delay flow separation), it will most likely reduce drag.

 

[rcgldr]

The purpose of vortex generators is to trigger the transition from laminar to turbulent flow at a specific point. Turbulent flow can reattach and/or remain attached for longer over a convex surface. I don't know if the flow under a typical race car is laminar or not. The purpose of the rear diffuser is to provide an expanding cross sectional area for the lower pressure higher velocity (with respect to the car) air under the car towards ambient pressure at lower velocity.

Formula 1 race cars are not allowed to use under body aerodynamics, and have a skid board underneath used to check that the cars are not lowered beyond what the rules allow. Indy Racing League cars do use under body aerodynamics in addition to wings, but I don't know if they use vortex generators. Nascar race cars use a splitter up front, an air dam under and near the front, block off the front vent based on conditions to reduce flow through the engine compartment and under the car, based on how hot the ambient temperature is (if it's hotter, less tape can be used) and a spoiler at the rear. Nascars tried using wings at the rear, but are now back to using spoilers.

 

[Iceracer33]

The purpose of vortex generators is to trigger the transition from laminar to turbulent flow at a specific point. Turbulent flow can reattach and/or remain attached for longer over a convex surface.

Reference https://www.physicsforums.com/threads/vortex-generators-under-your-racecar-question.924227/

So the trailing edge of the front splitter would be the best place? This will delay the flow from reattaching until it hits the rear diffuser? I believe that the vg will help the air from not bouncing around off the exhaust and stuff as well which will make the rear diffuser work better.
Oh and racecars have rules to abide by, I have no rules, only experimentation. F1 also uses vgs all over their cars to make sure no disturbed air reaches the rear splitter.

 

[Ranger Mike]

Got over 100 of these all over the Dodge Cummins 1 ton pickup and 30 ft trailer...saves 2 MPG

http://www.airtab.com

 

[rcgldr]

So the trailing edge of the front splitter would be the best place? This will delay the flow from reattaching until it hits the rear diffuser? I believe that the vg will help the air from not bouncing around off the exhaust and stuff as well which will make the rear diffuser work better.
Oh and racecars have rules to abide by, I have no rules, only experimentation. F1 also uses vgs all over their cars to make sure no disturbed air reaches the rear splitter.

Form what I can find at various web sites, F1 vgs are mostly on the upper surfaces of stuff like front wings, side pods, and apparently only on the bottom surfaces of stuff like the rear diffuser. I doubt underbody flow separation is an issue because there's no place for the flow to form a bubble (the pavement prevents that). Nascar uses canards (like small wings) on the front bumper to induce vortice (rotational) flow along the sides to act somewhat like an aerodynamic wall to reduce flow from the sides to under the car. I don't know if open wheel cars use something similar.