Static and dynamic roll stability analysis of a semi-displacement fast ship

The flow field generated by the towing of a semidisplacement hull, free to heave and pitch, is numerically investigated in the velocity range 18 - 34 Kn. The effect of an imposed roll angle have been studied for 4o , 6o and 8o and for three velocities (namely: 20, 24 and 28 Kn). The numerical code adopted is the in-house developed Xnavis, which is a general purpose unsteady RANS based solver; the solver is based on a Finite Volume approach together with a Chimera technique for overlapping grids and a Level Set approach to handle the air/water interface. The generated wave pattern shows many interesting features with an evident wave plunging near the hull bow, while the stern remains completely dry for velocities over 30 Kn. The numerical outcomes are discussed in terms of forces and attitudes.