Rolling motions is something that is undesired in all kinds of seafaring. In terms of propulsion resistance, comfort and route planning it would be desirable to reduce these motions.
This study is an investigation on how different roll stabilising systems affect the performance of an 8000 unit PCTC vessel, special emphasis is put on investigating the performance of anti roll tanks. The ship in question has a recorded incidence of parametric rolling and the ability of the tanks to countervail this phenomenon is also investigated.
The tank and fin stabilising systems are relatively equal when it comes to roll damping performance related to changes in the required forward propulsion power. The tanks however, have a higher potential for improvements, addition of features such as heeling systems and parametric roll prevention systems.
The tank performance is also independent of the speed of the ship. The tanks are easier to retrofit and do not require the ship to be put in dry dock during installation. The conclusion of this thesis is that a combined anti roll and heeling system should be installed but that a further study has to be made on the performance of active rudder stabilisation.
It is shown that passive tanks are efficient at preventing parametric rolling in some sea states. A proposal is made for a further study on a control system that could achieve the same performance for all sea states.
Author: Windén, Björn