Unsteady RANS CFD simulations of ship manoeuvrability and course keeping control under various wave height conditions

Ships encounter different wave heights in real sea states. Various wave heights can lead to substantial changes in the behaviour of a ship during manoeuvring, and hence a ship's manoeuvrability in waves should be accurately evaluated to ensure navigational safety at sea. The aim of this study is to estimate wave height effects on the manoeuvring behaviour of the benchmarking KRISO Container Ship (KCS) model by performing a fully nonlinear unsteady RANS simulation. Three types of manoeuvres were simulated with the free-running KCS model appended with an actuator disk and a moving semi-balanced horn rudder using a dynamic overset technique: self-propulsion, course keeping control, and turning circle manoeuvres. Manoeuvring analyses were carried out in the bow quartering waves of a range of wave heights for constant wave length, as coupled with the fifth-order Stokes wave model. In order to control the rudder deflection based on manoeuvre mechanisms, a feedback controller was embedded in the present CFD model. The results clearly revealed that wave heights have a strong effect on the manoeuvring behaviour of the KCS, including ship's speeds, seakeeping behaviour, and critical turning indices through comparative analyses under different wave height conditions. One important finding is the standard manoeuvring parameters in waves, which would help navigation officers in decision-making for manoeuvring actions in waves.