Controlling the Roll Responses of Volume Carriers

Sammanfattning: Modern volume carriers such as container vessels, cruise ships and Pure Car and Truck Carriers (PCTC’s) have become more vulnerable to critical roll responses as built in margins have been traded against increased transport efficiency. The research presented in this doctoral thesis aims at enhancing the predictability and control of these critical roll responses. The thesis presents a holistic framework for predicting and assessing the roll damping, which is a crucial parameter for predicting roll motions, based on a unique combination of full scale trials, model tests, semi-empirical methods and computational fluid dynamics. The framework is intended to be used from the early design stage and gradually improved until delivery of the ship and finally to provide input for decision support in the operation. The thesis also includes a demonstration of a new application for rudder control to be used for mitigation of parametric roll. This is performed by simulating real incidents that have occurred with PCTC’s in service. Simulations with rudder roll control show promising results and reveal that the approach could be very efficient for mitigation of parametric roll. Finally, an approach for monitoring of roll induced stresses, so-called racking stresses in PCTC’s, is presented. The approach involves measurement of the ship motions and scaling of pre-calculated structural responses from global finite element analysis. Based on full scale motion and stress measurements from a PCTC in-service the approach is evaluated and demonstrated to be an efficient alternative to conventional methods.