on 8/23/02 4:20 PM, Clive Smith wrote:

>
> I did say, just be aware.....
> and I think if you look back through the mails, you'll find it was me that
> first suggested tufting!

Maybe you did Clive, but I think I posted something along the same lines
(yarn etc) back in 95-96. But what the heck.

> ...and if I spent my time sitting on my duff, I wouldn't know what you
> obviously don't: that to a fly, the air's like treacle which is why they can
> change direction and accelerate away from your swat quicker than you can
> swing it.

I do understand the concept that the Reynolds number serves to measure. And
Clive, re-read your fly comments above, you might find an inconsistency or
at least an interesting notion.

No I can't resist...air is not like treacle to a fly. If it were when you
dropped a dead fly it would take more than a few minutes to hit the floor.
Well I know that is not true, seen flies drop, played with treacle.

Or do you mean the fly's wings? I dunno, I guess you know what you mean.

Try instead the interesting world of the microbe (if you have the wit). A
bacterium of approx. 2 long and 1 micron in diameter swimming/flagellating
through water is approx. like us swimming through warm asphalt. When it
stops "swimming" it coast for a very/extremely small fraction of its body
length, in essence stops dead immediately.

And why to a Pterordactyl or a hang glider the air appears
> somewhat less sticky, and less thick too if you have the wit to imagine
> being an airliner at 500 mph and 7 miles up.

Gee, no, can't do that Clive, well out of the range of my feeble wit.

> Thats what Reynolds No is about... Speed x Length /Viscosity - no units.
>
> and yes, NO relation, unless you run the tunnel at model scaled Re Nos.
> and if you want to

Make up your mind, relationship or not?

>> ... at least visualise the flow around the van in a gross way...
>
> .. find a big smoky fire near a roadside and drive through it while a mate
> on the roadside videos it.
> ...or drive behind aVanagon thats burning oil or smoking bad (or use a smoke
> cannister up front), and watch those Karman vortex wakes - most flat backed
> vehicles have a very predictable flow pattern, the important thing is when
> the flow suddenly changes its overall character, maybe 20, maybe 60 mph -
> that is what Reynolds No determines.

Did I say I wanted to see just vortexes at the rear? Well I guess you know
best.

> .. but I won't go on and explain further, as it appears you know what you
> know and don't much want to know what you don't.

Thanks again, such a benefit to have you on the list, now I know what I
don't want to know.

Alistair (I think, although maybe I don't know...but I do know this thread
is dead for me)

>
> Clive
> '88 Syncro Transporter