On the application of empiric methods for prediction of ship manoeuvring properties and associated uncertainties

In relation to development of ship manoeuvrability standards, in particular those accounting for adverse weather conditions there is a need for relatively simple but reliable prediction methods. A number of popular published empiric methods for predicting manoeuvring properties of surface displacement ships have been briefly described and analysed. An extension of the Pershitz method to low speed manoeuvres has been implemented. Sixteen empiric methods and hybridizing combinations of hull and rudder sub-models were tested numerically through simulation of standard manoeuvres for the KVLCC2 benchmark ship. The obtained numerical results have demonstrated that very few methods or combinations give reasonably accurate results for this vessel and some simulated responses even look unacceptable. The primary conclusion drawn from the study is that in general application of universal empiric methods can lead to unacceptably large prediction uncertainties and such methods must be used with great care and preferably tuned on prototype ships.