Downforce calculation Equation

[FW17]

Some info on the R18 (old one) wind tunnel data

http://www.mulsannescorner.com/newsnov10.html

[Speed_Demon]

I only ever seen this formula in metric measurements??? Does anybody have one in standard units (sq/ft. , lbs)?

[rscsr]

I only ever seen this formula in metric measurements??? Does anybody have one in standard units (sq/ft. , lbs)?

You do realize that the standard units for anything scientific is the metric system and not the imperial.
But nonetheless you can just get it yourself.
1m=3.28084ft
1kg=2.20462lbs
so with this you can "replace" every meter and kg in the formula and you get the factor you have to multiply the result of your units to get the real result. (7.233 in this case, because the result is [m*kg/s²]=[3.28ft*2.20lbs/s²]=[7.233*ft*lbs/s²]=[N])

[Speed_Demon]

I only ever seen this formula in metric measurements??? Does anybody have one in standard units (sq/ft. , lbs)?

You do realize that the standard units for anything scientific is the metric system and not the imperial.
But nonetheless you can just get it yourself.
1m=3.28084ft
1kg=2.20462lbs
so with this you can "replace" every meter and kg in the formula and you get the factor you have to multiply the result of your units to get the real result. (7.233 in this case, because the result is [m*kg/s²]=[3.28ft*2.20lbs/s²]=[7.233*ft*lbs/s²]=[N])

I wasn't looking for conversion factors....just a complete standard equations. Converting to metric, just to enter into and equation, only to convert it back is a little redundant. Most sports car downforce #s in magazines are given in lbs. so I wanted to keep it lbs for comparison sake.

[elpelucas]

It is based on purely experimental values, there is no way to determine downforce unless using a CFD solver / wind tunnel.

[Speed_Demon]

It is based on purely experimental values, there is no way to determine downforce unless using a CFD solver / wind tunnel.

True as how it would interact with the vehicles body would affect the result. The only standard formula I've seen, "racecar aerodynamics book" was lift lbs = .00256 *CL*wing area (sq.ft.)*mph(squared)..it seemed to simplified as it didn't have a factor for the air density or AoA. I guess the formula assumed standard atomospheric conditions at sea level and that the cl was at that angle (from a CL/alpha graph)?

[Just_a_fan]

Most sports car downforce #s in magazines are given in lbs. so I wanted to keep it lbs for comparison sake.

N, or at (an incorrect) stretch kg, seem most common. Except in the US, of course.

[Greg Locock]

The .00256 bundles in all the conversion factors and the air density. CL is being treated like Cd, a single number not a gain.

Incidentally the original equation from Wiki at the start of this thread wasn't wrong, just misinterpreted. H was the section thickness, not height off the ground. However I don't think ground effect wings operate in the regime where lift is proportional to alpha.