MODELING AND CONTROL OF UNDERWAY REPLENISHMENT OPERATIONS IN CALM WATER

Ship-to-ship operations, such as underway replenishment (UNREP), lightering, etc., entail potentially hazardous situations due to the possibility of collisions between two ships operating in close proximity. In order to ensure safe joint operations with collision avoidance, knowledge of the hydrodynamic interaction loads between the two vessels is highly advantageous. This paper thus considers the hydrodynamic interaction effects between two advancing ships and their maneuvering behaviors in calm water during typical replenishment operations. For this purpose, a unified seakeeping and maneuvering model of two interacting ships based on a two-time scales and modular concept relevant for calm water is employed. The maneuvering module is based on generalized slender-body theory, while calm-water interaction forces and moments between the two ships are estimated using Newman-Tuck theory. Automatic steering and speed control algorithms for both ships are also employed to achieve high-precision and collision-free UNREP maneuvers, which is illustrated through a numerical simulation involving the well-known “ESSO OSAKA’ and “MARINER’ models from the ship literature.