I can't find good explanation of Flume Tanks [Archive]

Squidly-Diddly

08-02-2009, 10:14 PM

http://pws.prserv.net/flume/flumetankstabilizers.htm

I take it they aren't actively pumping water from tank to tank to counter rolling.

Are they just a tank of certain shape that is half full of water and that spans the beam?

Do they have baffles?

Any good sites that explain them?

jehardiman

08-03-2009, 10:49 AM

Basicly they are a damped pendulum tuned to be opposide the roll.

The system is two tanks, filled with a given volume of water connected by a duct of fixed size with or without a pressure regulating system for the tanks.

At rest, the water in the tanks is evenly split between the two as the water seeks it's own level. During rolling, water attemps to flow from the high side tank to the low side tank, but cannot flow quickly because of the regulation of the connecting duct as well as the distance to move the CM of the water. This causes a wave system in the tank with a given period regulated by the volume of water in the tank. By judicious control of the water volume and possibly pressure, the tank set can be made so the "low" tank just fills to maximum as the ship starts its roll back. This keeps weight on the new "high" side during the upward roll, damping the roll.

It is important to remember that passive anti-roll tanks actualy reduce both initial and absolute stability and therefore must be considered in the stability calculations. In this way they are considerably different from active systems. Additionally, flume style anti-roll tanks can have considerable structural loading due to internal wave slap.

The "U-tube" type of anti-roll tanks mentioned in the cited advertisement are simuliar except the duct/pipe between the tanks normally contains a flow regulating valve or device. Additionally, there are some other things stated in that advertisement that are not exactly correct when comparing the two types of anti-roll tanks. DNBEYR. YMMV.