Dynamical features of an autonomous two-body floating system

Dynamical aspects of a system composed by two interconnected ships floating at sea under the combined action of wind and current are presented here. Realistic, simulation-type, mathematical models are used throughout to represent the hydrodynamic and aerodynamic interactions of the vessels with their environment, as well as to incorporate the restoring forces from mooring lines and connecting hawser. A numerical study reveals that the system can have several theoretical equilibrium positions (up to fourteen), which can be stable (attracting) or unstable, feasible or geometrically impossible (implying superposition of the hulls). The system is also shown to exhibit attracting limit cycles. It is demonstrated that the number of solutions and their stability properties depend on various system parameters such as the wind to current speed ratio, wind and current angles of incidence, and shuttle vessel’s draft. The role of the wind to current speed ratio and of wind angles of incidence is examined in detail, allowing the construction of a series of bifurcation diagrams in which stability properties as well as physical feasibility are identified.