Quote:
Originally Posted by 3-Wheeler
Hi Aerohead,
Apparently the ISO paper must have some other variables besides the absolute temperature that affects your calculated 18% increase in drag.
If the air drag increase was strictly based on temperature (air density), then the variation between 70°F and -20°F would be:
= (460°R + 70°F) / (460°R + (-20°F))
= (530) / (440)
= 20.5%
Jim.
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Jim,many of the densities were tabulated in my fluids text.For the others I found the specific weight at given temps( at standard pressure) and divided by the gravitational constant to get rho.Everything is calculated at Standard barometric pressure.
Some of the tabular data I ignored,as it dealt with elevations we'd never encounter in a vehicle.- 12.3 degrees is not encountered until 20,000 feet. - 20 degrees is up where commercial aircraft are operating.
The data I have must reflect temps/densities impacted by meteorological effects.
I'm hamstrung here at the copy center asI don't have all my notes with me.If I'm off base I apologize and will dig back in when I get home and rectify.
I'm also going to post a table on temp/elevation and baro. pressure/elevation.If you can shoot some holes in those let me know,as things are tough enough as it is let alone going down some dead-end path.
I appreciate the heads-up.