In the present work, numerical simulations of standard zigzag maneuver in both calm water and waves are performed. The fully appended ONR Tumblehome model is applied for all the numerical calculations. In-house CFD solver naoe-FOAM-SJTU is used for the direct computations of free running ship model with rotating propellers and moving rudders. Dynamic overset grid method is applied to handle with the complex ship motions with propellers and rudders. Open FOAM's third party library waves2Foam is used for the wave generation. Standard 10/10 zigzag maneuver at the approaching speed of Fr=0.2 in calm water and regular head waves are simulated. Ship motions, speeds, propulsion forces and main parameters of standard zigzag maneuver are obtained and compared with the available experimental measurements. Furthermore, flow visualizations are presented for better understanding of the hydrodynamic performance during zigzag motion. Satisfactory agreements are achieved and indicate that the present CFD method with overset grid technology is feasible for the direct simulation of zigzag maneuver in both calm water and waves.
Ship maneuvering is closely related to the navigational safety and this concept lead to the IMO criteria (2002) for ship maneuvering performance. Thus how to accurately predict the ship maneuvering capabilities at the design stage is of great importance. Among several approaches to predict ship maneuverability, direct simulation of free running ship model with rotating propellers and moving rudders is the most accurate way to reappear the real flow field during ship maneuvering motion. However, great challenges show up with the complexity of the flow field and interaction between hull, moving rudders and rotating propellers. When dealing with the fully appended ship, the vortical structures separated from the hull and appendages are even more complicated. For most simulations in ship hydrodynamics, the 6 degrees of freedom (6DoF) motion is always simplified into 3DoF (roll, heave and pitch) or 2DoF (heave and pitch), which is enough to handle ship resistance, seakeeping problems (Bhushan et al., 2009). But for free running ship maneuver, i.e. turning circle maneuver and zigzag maneuver, the ship needs full 6DoF motion with active rudders and rotating propellers in a free surface condition. All the above aspects increase the difficulty in the study of the free maneuvering problems.
