The best way of reducing roll motion is by increasing roll damping. Bilge keels are the most common devices for increasing roll damping. If more control is required, anti-roll tanks and fins are used. Tanks have the advantage of being able to function when the ship ist not underway. Our objective is to develop design procedures for passive tanks for roll reduction in rough seas. This paper focusses on the design of passive U-tube tanks. The tank-liquid equation of motion is integrated simultaneously with the six-degree-of-freedom (6DOF) equations of the ship motion. The coupled set of equations is solved by using the Large Amplitude Motion Program 'Lamp', which is a three-dimensional time-domain simulation of the motion of ships in waves. The unstabilized roll motions of a S60-70 ship with forward speed and beam waves have been analyzed. For high-amplitude waves, the unstabilized roll angle exhibits typical nonlinear phenomena: a shift in the resonance frequency, multi-valued responses, and jumps. The performance of a S60-70 ship with a passive tank is investigated in various sea states with different encounter wave direction. It is found that passive anti-roll tanks tuned in linear or nonlinear ranges are very effective in reducing the roll motion in the nonlinear range. The effect of the tank damping, frequency, and mass of the tanks performance is studied. Also, it is found that passive anti-roll tanks are very effective in reducing the roll motion for ships having a pitch freqency that is nearly twice the roll frequency in sea states 5 and 6.
Design of passive anti-roll tanks for roll stabilization in the nonlinear range
Der Entwurf von passiven Rolldämpfungstanks für die Stabilisierung der Rollbewegung im nichtlinearen Bereich
Ocean Engineering ; 29 , 2 ; 177-192
2002
16 Seiten, 15 Bilder, 19 Quellen
Article (Journal)
English
Roll stabilization by anti-roll passive tanks
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