Ship manoeuvring in shallow and confined water

Mooring

With ships getting larger, the safety of (large) moored ships is becoming increasingly important. This concerns both mooring line and fender forces, as well as ship motions. PIANC has established two working groups working on 'safe mooring of large ships at quay walls' ( WG186) and 'update of WG24 - criteria for acceptable movement of ships at berths' ( WG212), both of which the department is involved in.

Moored vessels are subjected to external forces of various origins, which are always location dependant, leading to custom studies for each terminal. The external forces include environmental forces (wind, waves, current), as well as passing ship effects. Most services provided by Ghent University up to this day include berth areas which are sheltered from waves (e.g. estuary Scheldt - Antwerp), yet suffer from large wind forces and passing vessel effects. These dynamic mooring analyses (DMA) are performed using the in-house time-domain simulation software Vlugmoor.

Examples

The department's work focusses on providing expert services, which are often leading to (indirect) publications. These projects also identify gaps in existing knowledge, which are then subject of dedicated research work. Some examples of the work are given below, with references are included in case the work has been published.

• For the Port of Antwerp area, several studies have been performed to evaluate the effect of passing ships on moored ships in restricted channels. The Port Authority also provided full scale motion measurements, which have been used for model validation. [Van Zwijnsvoorde, T.; Vantorre, M; Ides, S, 'Container ships moored at the port of Antwerp : Modelling response to passing vessels', PIANC World Congress Panama City, 2018]
• Since ships (gas carriers, RoRo, container ships) are getting larger, passing events become increasingly critical for existing channel dimensions. Numerical predictions reach their limitations in these cases. In order to produce a mathematical model to cope with these conditions, a dedicated model test program has been performed at Flanders Hydraulics Research in spring 2019, called PESCA (Passing Effects in Shallow and Confined Areas). The regression model based on these systematic tests will aid the department in accurately predicting passing ship forces, in today's but also in future cases.
• Incident cases where the moored ship's lines rendered and/or broke have been examined in detail, exposing the reasons for this unwanted event to occur. Rendering winches, as well as breaking lines were modelled in the software, as well as the tugs which were assisting in keeping the vessel moored.
• Literature and informal discussions also reveal that issues with mooring operations and/or inadequate mooring equipment can lead to safety being compromised. Examples here are absence of pretension / slack in lines [Van Zwijnsvoorde, T; Vantorre, M, 'Safe mooring of large container ships at quay walls subject to passing ship effects', Trans RINA, vol 159, part A4, Intl Maritime Eng, Oct-Dec 2017] and use of very elastic lines [Van Zwijnsvoorde, T; Eloot, K; Vantorre, M; Lataire, E, 'A mooring arrangement optimisation study', 11th International Workshop on Ship and Marine Hydrodynamics, Hamburg, Germany, September 22-25, 2019] .
• When dealing with passing ship effects, a standard well-balanced mooring configuration of a container ship at a quay wall can still be optimised, when it comes to mooring operation and ship design phase.
• Air draught and wind area of both cargo as well as passenger ships keep on increasing, which makes them more susceptible to wind effects. Wind forces are usually calculated using simplified formula, concealing the expertise behind them. This has been addressed in [Van Zwijnsvoorde, T; Donatini, L; Van Hoydonck, W, Lataire, E, 'Wind modeling for large container vessels : a critical review of the calculation procedure', Maritime Transport, Italy, Rome, 2019] , revealing potentially large errors with improper use of coefficients, e.g. with differences in wind profile for wind coming from land/sea.
• The effect of passing ships on bunkering ships moored next to large sea-going container ships has been evaluated. Results show that the phase difference in motion between both ships is an important factor contributing to line forces and motions of the bunker vessel.