CFD modelling and analysis of ship handling operations

The operational capability of ships to manoeuvre in restricted waters, e.g., in ports or channels, is challenging despite the development of control systems onboard ships. These risks reaffirm the role of the tugboat assistive operations in ports and channels under varying hydrometeorological conditions. This thesis presents a Reynolds Averaged Navier Stokes Computational Fluid Dynamics (RANS CFD) method that may be used for the evaluation of the contact forces acting on the tugboat and an assisted ship during pushing operations. The thesis suggests decision making charts that may aid tug masters during pushing operations. Two models are used to idealise ship dynamics during tug operations. The first model utilises the STARCCM+ solver, including an unsteady RANS method, the dynamic fluid body interaction module (DFBI), and the contact mechanics coupling module to model the contact between a tugboat and an assisted ship. The second model (tug-force equilibrium) applies the same solver with steady and unsteady RANS methods without the DFBI and the contact mechanics coupling modules. The contact force in the second model is calculated as a sum of the hydrodynamic forces on the hull and the propeller. It is demonstrated that the mean values of contact forces predicted by the two models are nearly similar, whereas the DFBI model can idealise the time variation of the contact force. The tug-force equilibrium model is shown to be more time-efficient in predicting the mean values of contact forces and for developing decision-making charts. It is concluded that the tugboat speed and orientation are vital and may amplify the pushing forces. Moreover, the pushing force at low speed might reach the bollard pull value and more when the hull forces supplement the force provided by thrusters i.e., when the sway force act on the negative direction relative to the tug-fixed coordinates, it amplifies the pushing force