wing section for inverted ground effect

[dalcazar]

I'm looking for the best possible airfoil out there for a wing-in-ground-effect section that is inverted in order to generate downforce, the airfoil has to generate as little drag as possible whilst maximizing downforce. The requirements are a bit of an oxymoron, but please advise on the best possible compromise or solution

 

[GregLocock]

It will be entirely dependent on the airflow around the other parts of the vehicle. How close to the ground? what is the chord and the span? Re?

Cheers

Greg Locock

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[dalcazar]

This is not for vehicular aplication so there will be no constant interfering airflow. Closeness to the surface will be dictated by the chord itself and should be around 20% of the chord. Span is a bit of a non-issue since the section will be variable over the span of the wing, as will the distance to the surface.

Right now I'm looking for different wing sections that I can use for a proof of concept model and reference material that has to do with ground effect and wing sections is very hard to come by.

Sorry I can't be more open about the application, but I don't want to disclose any details until I've filed for a patent.

 

[GregLocock]

OK, none of the standard airfoils will be 'the best possible'. So I'm afraid you are going to have to invent one. Re will be important as it will affect boundary layer thickness which has some impact on this sort of problem.

The aerodynamics of solar cars is very similar to this and small changes in the profile can cause a 30% shift in drag.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rb1957]

greg has raised several relevent points ...
span and chord do matter, it's called aspect ratio, and for your geometry the aspect ratio is 5.
all airfoils vary their Lift/Drag substantially with angle of attack, which i suspect is constant for your application.
reynold's number is an importantinput for airfoil selection. i suspect that in your case it's quite low, which isn't a problem, you just need to be aware of it.
why is the specific profile that important to your patent application ? surely the patent outlines an idea, the novel solution to a problem, the novel application of technology, without saying (necessarily) "using a NACA 0012 airfoil this patent does ..."; if you did then would could get around your patent by saying "using a NACA 0016 airfoil ..." no?
Research airfoil L/D ... incidence is important (constant though it may be) ... a NACA 0012has zero L/D at zero degrees (will it does in free stream aerodynamic situations, 'cause it's symetric and has zero lift at zero incidence; in ground effect the situation may be different) and something +ve at positive incidence.

 

[KENAT]

Um, if you're interested in down force why not at least look at the aerofoils sports/race cars use rather than trying to invert a WIGE.

Fundamentally the angle of the dangle is the most important part.

Depending on application, especiall if really rough Proof of Concept, I'd consider just a symetric aerofoil - essentially a stretched out tear drop shape.

KENAT,

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