Hey Jay, I trust your enjoying the fruits of the sugar cane. I agree with all you wrote below. Wow hows that for a good day. I wanted to add that since the sub would be moving upwards during an ascent, likely in a pretty level manor if its still balanced front to back. So one would need to make the flow of fluid over the model, from top to bottom, and then run a couple of other angles of attack. You gave me an idea that might do the trick. I may only need the relief valves at the surface, which is far easier to figure out. Since we are basically talking about a integrated lift bag system for blowing at depth in an emergency, what if I have a designated large valve(s) for when I'm blowing at depth, that have no relief valves on them at all. Just let the air freely flow thru the valve and down below the floats a little like you see on the large ABS pipe side MBT's on the Dennoch sub, with two tubes running down below them for letting the air out. Once back at the surface you can close the valves and add a little more compressed air to the floats to get them to the proper pressure. Your resident pipe dreamer ;)' Regards, Szybowski From: bottomgun@mindspring.com To: personal_submersibles@psubs.org Subject: RE: [PSUBS-MAILIST] Calculating Acceleration of a Subs Ascent Date: Fri, 5 Sep 2008 20:38:37 -0400 Brent, So now with your greater understanding of the issue you can realize some of the complexities of developing a safe solution. I believe you could calculate this acceleration and it shouldn’t be too difficult, it is for issues like this that I am back in school studying naval architecture. It might be solvable with your combination of FlowWorks and SolidWorks but not familiar with the particulars of the programs. You have to be very careful with modeling software because you have to know more than the program so that you can identify false solutions. While working on a flow study of Nahant Bay north of Boston in the late 70’s, two MIT grad students developed a theoretical flow model of the Bay looked great but when they ran it, a 75 ft. tall water spot mysteriously appeared in the middle of the Bay in the model. Care must be taken with finite element analysis (FEA) and computational fluid dynamics (CFD) so that you can identify what appears to be a correct solution that is indeed false.
I do know that FlowWorks is great for modeling complicated flows in piping and the path water takes along a moving hull but not sure that it is appropriate for your acceleration model (I qualify this once again in that I have not had the opportunity to work with the program). R/Jay
Jay K. Jeffries Andros Is., Bahamas
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
Hi Jay, Your resident pipe dreamer ;)'
From:
bottomgun@mindspring.com Brent, This goes against basic physics. If you have only a partial fill of a volume at depth, you will accelerate as you near the surface and pressure drops unless you can vent the expanding air (you will find this difficult as you manage all of the surfacing functions). You should always size your relief valves to be able to handle the maximum expansion rate. R/Jay
Respectfully, Jay K. Jeffries Andros Is., Bahamas
Talk sense to a fool and he calls you foolish. - Euripides (484 BC - 406 BC)
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
Your expanding air
filled dreamer ;)'
From:
brenthartwig@hotmail.com Your resident
pontoon dreamer ;)'
From: joeperkel@hotmail.com |