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Old 12-15-2008, 02:16 PM   #38 (permalink)
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Is it linear?

Originally Posted by NeilBlanchard View Post

Can you distill it down to an approximate percentage change in drag from say 75F down to 30F? Is it linear as the temperature drops, or is the change accelerated as the air temp drops?
Neil,since the density is in the numerator of the force and power formula,I think the change in density affects the results arithmetically,as a percentage of change.---------------------------- The density of air at 30-degrees F,under standard conditions is 0.002520 slugs/cubic foot.Dividing by 0.00238 gives a density 5.8% higher than at 59-degrees.The drag force according to the 1/2 rho Cd A V(squared) would increase 5.8% so it looks like a clean arithmetic relationship for us.'should be same in power calculation.------------------------------ I hope to post a table for those who do not have fluids text,which will list some data in the range we might expect to encounter over the course of a year.------------------------- P.S. A lot of other variables will also be changing with cooler temps and it is customary for us to expect at least a 3-mpg loss in winter driving.
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