COMPUTATION OF HYDRODYNAMIC FORCES FOR SHIP "ETNA" BY CFD TECHNIQUES

The activities aimed at the determination of hydrodynamic coefficients for the ship "ETNA", made in the framework of a contract between INSEAN and CETENA S.p.A., are described in the present report. These coefficients are those used in manoeuvrability simulation of a ship by means of ordinary differential equations where hydrodynamic forces are approximated as a functional relationship between the forces themselves and the motion parameters and their derivatives. In the following, the mathematical and numerical models, geometrical discretization techniques and the computer codes (all developed and implemented at INSEAN) are reported. Details of the surface and volume grid will be described. Then, all the numerical simulations carried out will be depicted in details, and in particular the following tests will be analysed . Steady drift . Steady rudder angle . Pure sway . Pure yaw . Yaw and sway combined The first two test programs have been performed by direct steady state simulations, whereas all the rest where carried out by unsteady calculations, of course. Test conditions where chosen to be the same as the ones used at DMI (Denmark) in 1998 [15] for towing tank tests. For all the simulations, both global quantities and field solutions (in terms of velocity vector and free surface elevation) will be reported. The data from numerical simulations will be compared with the analogous experimental data collected at DMI when available.