Manoeuvring model and simulation of the non-linear dynamic interaction between tethered ship and tug during escort

When dealing with towing and Escort operations – indissolubly – a wider and complete modelling of the involved dynamics becomes fundamental, on both ship and tug side, even more so making unavoidable the need of correctly ponder the cables constraining coupling. With the aim to better understand the peculiarities of tug-ship interaction, a 6-DOF time domain simulator comprehensive of the propulsion dynamics has been developed, across the inter-connection imposed by the towing-line. Particular attention is focused on discovering the operational capabilities of the tug in exerting a force on the assisted ship during Escort, and the subsequent great influence that the reaction makes on the tug handling and effectiveness. A conceptual and critical discussion stands out, preparing the ground to future design strategies and hinting different solutions to be investigated, directly facing the operative profile of the vessel.