James
Go to www.google.com and type in reynolds numbers, click on search and
have a ball, it's all there.
Glen
----- Original Message -----
From: "Waldron, James" <James.Waldron@CWUSA.COM>
To: <land-speed@autox.team.net>
Sent: Monday, January 21, 2002 1:31 PM
Subject: Reynolds numbers
> So, longer than I'd like to admit ago, when I studied this sort of thing
in
> college, I remember that there were two components to determining how fast
> something would go on a certain amount of power. One was the sum of the
> 'frictions' that had to be overcome (bearings, rolling resistance, etc.),
> and the other was the air resistance. When you were going slowly, the
first
> friction was the biggest, but as you started going faster and faster air
> resistance became the dominant player. Air resistance was cubic, related
to
> speed, and was determined by a 'Reynolds' number that related (it starts
> getting fuzzy here) the resistance of the shape of the object to an
> equivalent flat plate. Then something about a 1 foot square flat plate
> being some sort of standard. ANYWAY, I remember asking how Reynolds
> numbers could be determined and being told that it was way too complex to
> calculate and that most were determined experimentally by using scale
models
> in wind tunnels (and for cars, further complicated by the fact that the
body
> under investigation was close to the ground - not up in the sky - and the
> model ground had to move at speed to get real information, and after
> thinking about using my belt sander to simulate moving ground in the
college
> aerospace model wind tunnel, and the look I got from the dean when I told
> him I wanted to put a running belt sander with 80 grit sandpaper in the
wind
> tunnel and 'didn't think it could get loose'..... You get the picture.)
> So, what I want to know is, in this day of lots of computing horsepower on
> my desktop, are there any programs that can be fed a 3 dimensional object,
> can simulate air flow, and determine Reynolds numbers? And, of course,
I'd
> like to play with the design on-the-fly to see what needs to be done to
> minimize the drag. Or, are we still in the days of 'take it to the salt
and
> see what it will do?', record the speed and calculate to determine my own
> Reynolds number (if I still care at that point)? I know that the Americas
> Cup Yacht guys do lots of computer simulation, but also still use a scale
> model moving through a tank of water (water is a lot thicker than air, but
> except for compressibility, fluid dynamics should still apply?). Anyone
> have any sources of information?
>
> [demime 0.97c removed an attachment of type application/octet-stream which
had a name of Waldron, James.vcf]
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