Re: [PSUBS-MAILIST] fairings drag vrs entrained mass

[Paul Kreemer <paulkreemer@gmail.com>]

Yeah, it'd be great to test some models...  Regarding fairings, I haven't even checked the Busby book but was watching
the Russian Mirs recently on video and noticed how streamlined they
are.  I agree with EM that having flow through the fairing would
definitely increase your drag.  But I don't see a huge problem
with dragging the water around inside the fairing - at least within
reason.

And yeah, these speeds are pretty low but from the little math I did
you could see that streamlining does make a difference.  If you
want to hit 4 kts with something shaped like a pickup truck you need
more power than if you have a streamlined hull.


fun stuff!

On 11/28/05, EM <emuller@naic.edu> wrote:

Fairing is something I'm curious about too..
It seems to me that fairing defines a comoving volume that you have to
cart along, which really WILL affect the acceleration.. unless you allow
the water to flow THROUGH the fairing, which will just double your drag
(since you now have TWO surfaces exposed to the flow).

So you loose a lot with fairing. In one case you carry around a lot of
water, and your acceleration dies, in the other you just up your drag
(though hopefully the whole point of installing the fairing was to
re-divert flow away from lossy turbulent eddies etc.).

To be honest, the only use I can imagine for fairing is to re-divert the
flow away from potentially turbulent corners, and at the speeds
we're talking about.. is that often a big concern?

I think somone should make a flow-box.


EM.