Re: Air resistance

[John Mallinckrodt <ajmallinckro@CSUPomona.Edu>]

On Sat, 13 Dec 1997, brian whatcott wrote:

> I am rather more critical - I assert that no matter how far the data 
> acquisition is extended, you will not determine "n" with any precision
> using the present method, because it is not expressible as a constant
> with this method.
> ...

For the record, fundamentally, I agree with brian here.  Aerodynamic drag
is *very* complicated.  It is certainly misleading to describe it as a
"power law of velocity" and then patch it up with a velocity-*dependent*
drag coefficient as must be done if one wishes actually to express the
functional form of the drforce ag with any precision over a range of
velocities.

On the other hand, I suspect that the velocity-dependence of the drag
coefficient tends to be rather moderate over most velocity intervals
unless they happen to include transitions from viscous to dynamic drag or
other types of "drag crises" (as mentioned in the paper referred to by
Wolfgang Rueckner).  As a result, I'd still expect to get a pretty
reasonable fit with a power law like v^2.2, for instance, if the drag was
predominantly "dynamic" (i.e., n=2) in nature over the region of interest,
but the drag coefficient was slowly increasing with v. 

John
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