Three aft body shapes

Manoeuvring and course keeping in waves

To measure the crabbing performance, large models need to be used. The model on the photograph was the CRS base model for many crabbing tests in deep and shallow water

• MANWAV and MANWAV-2: methodologies to predict manoeuvring behaviour in waves

• MORE: manoeuvring in operational conditions.

The CRS working groups consist of scientists and practical ship designers. This interesting combination assures that not only fundamental research is carried out: at the end of the day, this always culminates in a software tool or prediction method. The resulting practical prediction method can be applied very rapidly, so that the ship designers can use them to create a manoeuvring prediction within 5 minutes.

What is the key to the CRS success? The beauty of the CRS model is that the developments are not curiosity-driven, but a direct consequence of developments in ship design. On one hand, designers had a direct need and on the other hand, the quirky scientists had opinions.

The MED project was driven by awareness that a full aft body had a detrimental effect on the course-keeping. The MAN project

was a direct consequence of the start of the development of the IMO requirements for ship manoeuvrability. The first non- mandatory A751 requirements became active in 1993, while the mandatory ones became active in 2003. MANTS occurred at the same time as the development of the larger cruise vessels (end of last century). MAN-3 was established following the introduction of the podded propulsor to the market. Even the latest developments regarding manoeuvring in waves (the MANWAV working groups) are occurring at the same time as the IMO required investigations related to the minimum power requirements for low powered ships. But also other ships need to demonstrate their ability to have adequate manoeuvring characteristics in waves and in wind nowadays.

The interesting part of the working groups is not only the result, but the way in which the result is achieved. The eclectic nature of the members of the working groups means that there is a good balance between applied research and practical applications in day-to-day work.

Since 2012, manoeuvring research of the CRS has also focused on special and unconventional manoeuvres such as acceleration turns and turn-on-the- spot manoeuvres. The manoeuvres in waves are of particular interest: course keeping, track keeping and the ability to turn. First, we developed knowledge and tools in the MANWAV project: insight into the autopilot, propeller loads and ventilation in waves, and the response of the engine to these. A large effort went into the investigation of the best way to quantify the 2nd order wave forces in irregular waves and the methodology to augment it to the manoeuvring simulations. Prior to the now selected solution, a fully coupled theory and de-coupled theory have been developed to investigate which would best suit the needs of the CRS. At last, the MORE project is applying and validating the simulation methodologies. Practical operational manoeuvres are simulated with the tool and validated with model tests on a ship while manoeuvring in waves (see also cover illustration).

report 29

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