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Re: [Phys-L] Dirigible Flight Question



On 11/05/2012 02:33 PM, Paul Nord wrote:

If I were able to plot "drag" vs. velocity what would I get?

I hate to sound defeatist, but it's not even a function!
That is to say, you can have more than one ordinate for
one abscissa. In the turbulent regime, a steady velocity
results in non-steady drag.

Is the function simply parabolic? (or rather abs(v) * v )

It's kinda sorta approximately parabolic over certain parts of
the range.

Will that fit most low velocities?

Absolutely not.

Is there also a linear term?

Yes ... and lots of other stuff. See e.g. figure 41-4 in Feynman
volume II.

===========

I assume everybody on this list owns at least one copy of the
Feynman lectures. Now would be a good time to re-read
volume II chapter 40 "The Flow of Dry Water"
volume II chapter 41 "The Flow of Wet Water"