This thesis attempts to investigate the effect of the implementation of Flettner rotors in the topology of the cruise ship Silja Serenade, which, in the year of this thesis dissertation, travels from Helsinki to Stockholm. The aim is the implementation of simulation models written in Matlab that simulate the behaviour of the ship topologies’ components, with the goal of minimising the global fuel consumption. The models refer to a particular time period defined by the provided data, but the structure is completely general and can be applied to the most different data and time periods, and for every ship. In the first part of this work, the literature part is described, covering the reasons of fuel consumption’s restrictions, the Flettner rotor’s old and recent history, the fundamentals of the ships’ topologies and a brief introduction to the optimisation theory.