Numerical Prediction Of Hull Force For Low Velocity Manoeuvring

In the last decades problems related to ship manoeuvrability have gained more importance in the context of naval architecture. Among them, problems related to slow speed manoeuvrability, such as port manoeuvres and dynamic positioning (DP), for which less data is available with respect to the conventional manoeuvrability at cruising speed, have taken more and more importance. The classical manoeuvring models have been developed to evaluate the ship force for high forward speed and low drift angle, therefore in case of slow speed manoeuvres, where high angle of attack must be taken into account, they do not provide accurate results. Despite the lower number of studies, also in this case different models have been proposed by various authors during years. The accuracy of codes to predict the ship manoeuvring capabilities are, obviously, strongly correlated with the accuracy of the prediction of the ship hydrodynamic forces, which are computed via regression formulae based, commonly, on existing experimental data. In the case of slow speed manoeuvring, unfortunately, only few data are available, representing an issue for the prediction of ship capabilities. In the present paper at first a comparison of different empirical models to evaluate the main ship force components for slow speed manoeuvring is presented. Then a RANS approach in order to tune coefficients for low velocity models has been explored, in order to evaluate its ability to compensate the lack of experimental data and provide a suitable alternative in the design phases.