Performance analysis of a motor-sailing propulsion system for control design purposes

This paper presents the simulation approach developed to evaluate the interaction between sailing and motor propulsion of a tall ship. In particular, the study is focused on the computational fluid dynamics (CFD) analysis of the wind thrust action on the sails. CFD modelling has been used because of the lack on scientific literature of the performance assessment of a square soft sail, especially if the interference among the several sails has to be considered. CFD results are discussed and then properly arranged to develop a propulsion simulator, able to provide interesting information on the whole ship performance. In sailing propulsion mode, it is worth paying attention also to the effect of the trailing propeller on the shaftline dynamics, mainly for reasons due to the efficiency reduction of the oil lubrication system at low revolutions. The final goal of the present work is to propose material and methods to find out and set up innovative control logics, in order to optimise the particular motor-sailing propulsion of the tall ships.