Natural period measurement of u-shape anti-roll lank using model experiment

U-shape anti-roll tank is an effective device to decrease the ship's roll motion, and it is appreciated for its simplidty, low cost and stabiiizing effect at iow speed or even zero speed. U-shape anti-roll tank consists of two tanks partially filled with water with the air spaces connected by a duct and a crossover duct at the tank bottom, and one valve is equipped in air duct to realize optimal stabilizing effect in most cases. In order to control the valve exactly, the natural period of U-shape anti-roll tank must be measured by effective methods. This paper disc" two mdmb based on model experiment from the point of view of practicability, and shows these methods can be used to measure the natural period of U-shape anti-roll tank exactly. Further study needs to put emphash on validating the stabilizing effect and improving tank design. the stabilizing effect of the U-tank is best in this condition. At other wave periods, the stabilizing effect is much less, and the increase of the roll motion of the ship even occurs at some wave periods. It is well known that the U-tank is equipped with a valve in air duct to realize optimal stabilizing effect in most cases. The most important problem is how to control the valve in different wave periods. One way is to determine optimal time period for closing and opening the valve refemng the natural period of the U-tank. In this paper, the natural period of the U-tank model was measured exactly by two experimental methods, so it becomes possible that the valve can be closed and opened with optimal time period aimed at producing the largest counteracting moment. The key problem realizing optimal control of the U-tank was solved very well.