Need: Wind force as function of frontal area and speed

[sprintcar]

Anyone have a spreadsheet showing the force produced by flat frontal area vs. vehicle speed?

I was trying to explain the effect of the large flat area on the front of a trailer at 70mph to a salesperson (to no avail) and I'd like to just equate it to pounds of force.

Thanks!

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein

 

[pyro]

It's just dynamic pressure (.5*rho*v^2) distributed over the frontal area, but there is also pressure drag (low press zone in wake) and parasitic drag from your 12' antenna.

 

[sreid]

The more complete answer to your question is

D = 0.5 x Cd x rho x V^2 x A

D = Drag-lb
Cd = Drag Coefficient-2 for low Reynolds numbers-Flat Plate
rho = Air density at STP = 0.002387 Slugs/ft^3
V = velocity-ft/sec
A = Area-ft^2

So the drag from a ft^2 plate at 60 MPH (88 ft/sec) is

D = 0.5 x 2 x 0.002387 x 88^2 x 1 = 18.5 lb.

 

[sprintcar]

Thanks sreid - that's exactly what I needed!
I can translate that into a percent of vehicle weight and then slope - like going up a hill - which should help explain the effect even better.

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein