In practice, to ensure an even (or otherwise pre-set) load distribution amongst the mooring lines, the tension in the mooring lines is in reality manually adjusted by winching in the ropes until the vessel is idle and equal tension exists in all mooring lines.
In MIKE 21 MA this is obtained numerically by running the simulation in convergence mode. When this mode is enabled a stop criteria based simulation is launched, which only takes mooring line impact, and the wind, current and drift forcings (e.g. low frequency forcings) into account.
In convergence mode it is not possible to include wave forcings (high frequency forcing).
When convergence mode is enabled, the dialog Convergence Parameters will be specifically available, where the stop criterias for this simulation mode is to be specified.
Note: If a convergence mode run is not executed prior to the final time-domain computation (final computation mode), the mooring system can cause the vessel to move. This will change the tension in each mooring line. For unbalanced mooring systems, the vessel response can be so significant that tension in some lines disappear completely. The subsequent vessel response in an incident wave/current/wind field will resultantly be significant different to specified design conditions and will most often be regarded as a serious flaw in the model setup.
