|
Could you explain this further? and give the full equation? john > Date: Fri, 1 Oct 2010 08:35:50 +0800 > From: piolenc@archivale.com > To: personal_submersibles@psubs.org > Subject: Re: [PSUBS-MAILIST] Electric Propulsion > > Hoerner's Fluid Dynamic Drag, Chapter 6 has what you need - specifically > the formula in the bottom left column of page 6-16. For a body with an > l/d of 5, the friction coefficient at high Reynolds numbers seems to be > about .003, so the overall drag coefficient based on frontal area will be > CsubDo = .09 + .003(15+3*sqrt(.2)) = .139 > For a body 50 feet long with a maximum diameter of 10 feet, this gives a > drag of 1.376 x 10^5 newtons at 30 knots, or about 30,000 lbf. > Power required is 2,150 hp. This would have to be divided by the > propulsive efficiency, which will be pretty high if the propeller is > centrally mounted on the tail of the body, to give net power required. > > Best, > Marc de Piolenc > > Archivale catalog: http://www.archivale.com/catalog > Polymath weblog: http://www.archivale.com/weblog > Translation services: http://www.proz.com/profile/639380 > Ducted fans: http://massflow.archivale.com/ > > On 9/30/2010 11:45 PM, ShellyDalg@aol.com wrote: > > In a message dated 9/29/2010 11:21:45 P.M. Eastern Daylight Time, > > irox@ix.netcom.com writes: > > > > The idea of 25-30Kts is rather infeasible with battery power > > alone (I will be happy to be proven wrong, of course). > > > > Although reaching a top speed of 30 knots while submerged isn't feasible > > without nuclear power, it would be a fun exercise to calculate. > > The Albacore hull would be the choice for it's overall drag numbers, but > > just how much horsepower is required to push one at 30 Knots ? > > Jon said 50 feet long ? That's a good number. Anybody know the formulas > > to calc this ? > > I remember the S101 and how much space was taken up for batteries. There > > wasn't much room left for people, for sure. > > With the required horsepower known we could figure out how many > > batteries it takes to push that hard for how long. Then get a percentage > > of displacement needed to supply that amount of power. > > My guess is it's over 90%. You're really looking at building a 50 foot > > torpedo if 30 knots is the goal. > > Might be fun to figure out though. > > Frank D. > > > > ************************************************************************ > ************************************************************************ > ************************************************************************ > The personal submersibles mailing list complies with the US Federal > CAN-SPAM Act of 2003. Your email address appears in our database > because either you, or someone you know, requested you receive messages > from our organization. > > If you want to be removed from this mailing list simply click on the > link below or send a blank email message to: > removeme-personal_submersibles@psubs.org > > Removal of your email address from this mailing list occurs by an > automated process and should be complete within five minutes of > our server receiving your request. > > PSUBS.ORG > PO Box 53 > Weare, NH 03281 > 603-529-1100 > ************************************************************************ > ************************************************************************ > ************************************************************************ > |