Manoeuvrability Assessment of Twin Shaft Ships by means of Open-Source Code

This study offers an interesting reflection and presents some original features in the calculation of the ship’s hydrodynamic derivatives and interaction factors. The main purposes of this work are: a Provide an overview of the complete calculation sequence from the conduction of virtual captive tests to manoeuvre simulation. Virtual captive tests are carried out by developing a simplified and innovative procedure to reduce the computational effort; b Extend and validate the calculation procedure of captive tests with roll angle. From these results, the coefficients for 4 DOF model are calculated and the effect on manoeuvre prediction is analysed; c Provide and validate numerical calculation methodologies for the main interaction factors (propeller - rudder and hull - propeller/rudder) and show the comparison between CFD coefficients and theoretical (or semi-empirical) ones implemented in the DITEN manoeuvre simulator; d In all cases, results from CFD are used in order to compare with results from semi-empirical models developed during years at DITEN, with the aim of acquiring an insight into the capability of both methods (CFD and semi-empirical) and their merits and shortcomings; furthermore, CFD results may be adopted, especially when applied systematically, to improve semi-empirical methods;