On Mon, 22 Mar 2004, P.Dooley wrote:

> OK, so the Vanagon has a fixed shape and a sphere has a fixed shape.
> Seems like what you are saying is the Cd is variable for a sphere but
> fixed for the Vanagon?

It will vary with the Reynolds number, which has more to do with the scale
involved and the fluid the object is moving through.  Your Vanagon doesn't
change size so its Cd is pretty much fixed.  However, a very small sphere
and a large one will exhibit different Cd.

You can see this effect in the way butterflies and insects fly -- they fly
as if the air were very thick and soupy, because on their scale, it sort
of is.

David Brodbeck, N8SRE
'82 Volkswagen Diesel Westfalia
'86 Volvo 240DL wagon