Seakeeping Behaviour of a Flettner Rotors-Propelled Catamaran in Beam Waves

Abstract

This paper deals with the seakeeping of a catamaran propelled by Flettner rotors. The case study is an energy ship. The prediction of the roll motion of such a ship is of particular interest since she will mostly sail in beam seas. We used a numerical model based on the boundary element method to deal with the interactions of the ship with waves. It is supplemented by a model for the aerodynamic damping effect due to the rotors, the gyroscopic effects from the rotors and by the ITTC correction for roll damping. In the present study, it has been assumed that the Flettner rotors can be modelled as a distribution of elementary airfoils whose lift and drag depend on the local apparent wind speed. Interaction effects between the rotors and between the hull and rotors have been neglected. Regular waves have been investigated. For the considered case study, it is found that the Flettner rotors can have a small destabilizing effect or a small stabilizing effect on the ship motion depending on the ship speed and the rotors’ rotational speed.