The hydrodynamic interaction induced by the complex flow around a ship maneuvering in restricted waters has a significant influence on navigation safety. In particular, when a ship moves in the vicinity of a bank, the hydrodynamic interaction forces caused by the bank effect can significantly affect the ship’s maneuverability. An efficient algorithm integrated in onboard systems or simulators for capturing the bank effect with fair accuracy would benefit navigation safety. In this study, an algorithm based on the potential-flow theory is presented for efficient calculation of ship-bank hydrodynamic interaction forces. Under the low Froude number assumption, the free surface boundary condition is approximated using the double-body model. A layer of sources is dynamically distributed on part of the seabed and bank in the vicinity of the ship to model the boundary conditions. The sinkage and trim are iteratively solved via hydrostatic balance, and the importance of including sinkage and trim is investigated. To validate the numerical method, a series of simulations with various configurations are carried out, and the results are compared with experiment and numerical results obtained with RANSE-based and Rankine source methods. The comparison and analysis show the accuracy of the method proposed in this paper satisfactory except for extreme shallow water cases.
Due to the advances in shipbuilding technology and the needs in the shipping industry, the ship dimensions have kept increasing, and so is the traffic in the ports, approach channels, and harbors. Increase in ship dimensions and traffic in restricted waterways results in challenges in waterway transportation safety. Safe maneuver of ships of overtaking and encounter is one of them. This paper addresses the problem of the path control of ships in parallel motion in restricted waters accounting for the hydrodynamic effects, in which, the path control with nonminimum phase zero dynamics is a major concern. A new output redefinition method has been developed to solve the nonminimum phase zero dynamics. With the assumption of low-frequency ship motion in restricted waters and the use of the output redefinition method, a new ship response equation is proposed. Based on the new ship response equation, a feedforward + PID control law has been developed to control ship parallel motion in restricted waters. Simulation results show good control effect in medium hydrodynamic interaction, the control law and ship response equation can enhance the safety of ships moving in restricted waters.
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