co_driver 
Quote:
Originally Posted by co_driver
Numbers to use:
L* = effective diameter of your car [1990 Firebird: (72.4" (width) * 49.8" (height) )^0.5 = ~60" = 1.53 m]
v = velocity [50 mph = 22.35 m/s]
'nu' = 1.6*10^5 m^2/s
Thus: Re = 1.53 * 22.35 / 1.6*10^5 = ~2,100,000
(*) Note:
A better reference would be the effective diameter rather than its length, as length is used for flat plates.
Now, on to making 2D renditions of vehicles I have once owned...

I'll plug my SW2 numbers in :
L* = effective diameter of my car
[1999 Saturn SW2: (
66.7" (width) *
54.5" (height) )^0.5 = ~60.29" => 1.53 m]
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Same as Firebird Example, so the rest of my numbers will be the same.
v50 = velocity [50 mph = 22.35 m/s]
v55 = velocity [55 mph = 24.59 m/s]
v60 = velocity [60 mph = 26.82 m/s]
v65 = velocity [65 mph = 29.06 m/s]
'nu' = 1.6*10^5 m^2/s
Thus: Re50 = 1.53 * 22.35 / 1.6*10^5 =
~2,140,000
Thus: Re55 = 1.53 * 24.59 / 1.6*10^5 =
~2,350,000
Thus: Re60 = 1.53 * 26.82 / 1.6*10^5 =
~2,560,000
Thus: Re65 = 1.53 * 29.06 / 1.6*10^5 =
~2,780,000
I've been using 2,500,000 for my second run, so that means I've been calculating for a little under 60 MPH.
Based on the above, I have attached a supersimple Reynolds Number calculator using Microsoft Excel. Enjoy!
CarloSW2