In Step 2 the passing ship forces on the moored vessels were derived using the 3D potential code ROPES (Results On Passing Effect Ships). The outcome of these calculations, consisting of a time-series of passing forces, were used to determine the forces in the mooring system of the vessel. This was done in a dynamic mooring analysis using MARIN’s aNySIM XMF (Extensible Modelling Framework) which takes into account the non-linearity in the mooring system, as well as the dynamic excitation forces, consisting of passing ship forces and dynamic wind gusts. Based on the calculations, the normative moored ship and maximum passing speed, were identified.


Encounter manoeuvres deploying an auto-pilot Meanwhile, fast-time manoeuvring simulations on desktop computers (Step 3) were conducted in which the inbound and outbound vessel were simulated and controlled by an auto-pilot during an encounter manoeuvre. The auto-pilot steers along a predefined track, executing propeller, rudder and tug commands. The tug commands controlled the forward speed (escort mode) and the drift. Interaction forces between the vessels


during the encounter were calculated in real-time from parallel computations based on potential flow.


The results of the fast-time simulations were discussed with the pilots in order to establish a full mission simulation programme (Step 4) for the most challenging manoeuvres. Real-time simulations were then conducted by pilots using MARIN’s Full Mission Bridge simulators. The outcome of the simulations was assessed taking the professional view of the pilots into account, as well as numerical data describing the manoeuvres. Again, these simulations indicated that there are possibilities to encounter in front of the lightering location, but that pilots in practice, prefer to avoid these manoeuvres.


aNySIM XMF is a time domain software tool that simulates the motions of both stationary offshore vessels and sailing ships. aNySIM computes the motions of these vessels resulting from non-linear hydrodynamic and mechanical loading. The modular structure of aNySIM XMF makes it easy to combine different functionalities to model simple to complex configurations. www.marin.nl/anysim


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