Re: [PSUBS-MAILIST] hydrodynamics question

[Michael Holt <mholt@richmond.edu>]

Alec Smyth wrote:
> 
> My design has twin props astern, in tunnels fed by side-scoops (a la fighter
> jet). I'm currently making the mold for the stern fairing, and I'm
> contemplating the best size and shape for the scoops. Given that water is
> essentially incompressible, am I correct to assume the frontal area of the
> scoops should be the same as the area of the prop tunnels? Another
> possibility would be to eliminate the scoops altogether and go with NACA
> intakes or such. But the scoops are definitely sexier.

Keep in mind that NACA intakes or scoops will ingest all sorts
of floating stuff.  You're gonna have to find a way to screen
them -- probably with bars parallel to the flow, because real
screens would add significant drag.

I have here a paper on pumpjet design.  It's from "Underwater
Missle Propulsion," editied by Leornard Greiner and published
in the 60s by Compass Publications.    If you're interested,
I can try to have it scanned.

I'd like to see pictures of what you're doing, too.





Mike H.