Re: [PSUBS-MAILIST] Pipe Diameter (was RE: payload)

[Andy Jensen <drewacard@charter.net>]

That sounds right below is Pascal’s Principle that explains it a little better then I could.

http://www.grc.nasa.gov/WWW/K-12/WindTunnel/Activities/Pascals_principle.html

Andy J


Yes. On a three square-inch surface area of the sub, that would be perfectly true. But the pressure around the sub would not be changed: It would still be 267psi.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

The recent delay in the posting of emails (that, long with a few cups of coffee) has me rethinking this whole thing. And Frank, if I've come across in my emails as sounding condescending, I sincerely apologize.  My intent is not to challenge, merely understand.

Let me see if I can ask this a different way, and see what kind of answers I get (and yes, I am looking for answers)

If I had a square tube welded to the side of my hull, and the opening was exactly one inch wide by one inch high, and I had a square rod that fit perfectly inside this tube, then when the sub is 600 feet down, them amount of pressure I would have to exert on the rod (to keep it in place) would be 267 pounds because the end of the rod that is facing the ocean has one square inch of surface area.

Now, instead of a 1 square-inch example, I perform the same experiment with a �� tube & rod combination.  The total amount of surface area facing the ocean is a quarter of the surface area on the one-inch rod, so the pressure I would need to keep this rod in place would be about 67 pounds.

Now, let�s set up a third experiment: Let�s use that same 1� square tube, but this time we�ll weld a plate over the end (facing the ocean) that has a �� square hole in it. Now� how much force is it going to take to keep that 1� rod in the tube? My money would be on 267 pounds.

Here�s my idea of thinking: If you�re using a piston-type pump to force water out of the sub into the surrounding sea, the amount of force required is equal to the external pressure times the surface area of the top of the piston. I don�t believe it has anything to do with the diameter of the pipe between the pump and the hull of the sub.

Could someone tell me if I�m right or wrong on this one?

-- NP




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