CONVERSION FACTOR? - Pressure vs. Speed

[ramius-ii]

Hi All]http://www.subcommittee.com/forum/icon_smile.gif[/img]
How do you convert incomming water pressure in PSI to speed?

That is, as your sub travels through the water there is a certain amount of (resistance) pressure on the bow of the sub. if you were to measure this pressure in PSI (maybe 0-5), how would this equate to speed?

Thanks, Ed

[feet wet]

Wow Ed, What a question!

Wow Ed, What a question! First the psi is going to change with the depth the boat is at. The point of measurement will change the reading as well. Any current running will affect this. ect ect ect .
I have a distance/speed chart from an old mag that is set-up for different scales. Time over set distance= speed .If you want I'll fax you a copy.
Cheers
Jonathan Eno

[safrole]

I think the "speedometer" on

I think the "speedometer" on your average ski boat is basically a pressure gauge. I know that doesn't answer the question, but it could spur someone else.

[ramius-ii]

Thank you guys. http://www.subcommittee.com/forum/icon_smile.gif


Thank you guys.
I did manage to get the answer from Volker Groebi who writes articles for the Subcommittee report. If your interested, the answer is: "water is at speed already acting as a solid body (compression excluded). Ram pressure - what a speed sensor would measure - is 1/2 rho * v*v with rho = the density of the medium (fresh water at medium temperatures = 1) and v = velocity of the sub. So, a sub travelling at 0.5 m/s would create a pressure at the sensor of some 0.125 Pascal, equalling 0.0125 milliBar. 1 Bar = 15 psi 0.0125 mBar = 0.188 psi for 1 m/s". To compensate for depth changes, a differential pressure sensor with one side to incomming pressure and the other to static pressure would "self compensate" for changes in depth. Similar to indicated air speed in an aircraft.

Best, Ed

[rockpile]

]

[color=#000000]]