Re: [Phys-L] Dirigible Flight Question

[Paul Nord <paul.nord@valpo.edu>]

I'll take that as a, "yes."

I'm really looking at the point where the velocity goes to zero.  I'm sure that there are chaotic regions of turbulent flow where this function is no longer one-to-one and onto.  Near zero velocity there is no "drag."  There is only mass.

I do have volumes II and III.  Apparently the bookstore sells a lot more copies of volume I.  It wasn't in stock when I got my copy.

Paul


On Nov 5, 2012, at 3:53 PM, John Denker <jsd@av8n.com> wrote:

> 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"