Free running CFD simulations to investigate ship manoeuvrability in waves

Ship manoeuvrability is closely related to the safety of ship operation in a real seaway; therefore predicting a ship’s manoeuvring characteristics is of great importance. However, estimating a ship’s manoeuvring performance in waves is challenging because of the complex fluid-structure interactions between hull, rudder, propeller and waves. Traditional methods for the study of a ship’s manoeuvrability in waves, based on mathematical models combined with potential flow theory, cannot accurately and effectively incorporate the effect of waves on a ship. On the other hand, unsteady Reynolds-Averaged Navier-Stokes (RANS) computations are capable of resolving the interactions between a ship and waves with high accuracy. The main objective of this study is to carry out a fully nonlinear unsteady RANS simulation to predict the manoeuvring behaviour of a KRISO Container ship (KCS) model in different wave conditions. A dynamic overset grid method was used with the purpose of resolving large ship motions and rudder movement. A course keeping and manoeuvring control module based on a feedback control system was embedded in the simulation to control rudder deflection according to standard manoeuvre mechanisms. Simulation results were compared with available experimental data and showed good agreement, which demonstrates that CFD is a reliable approach to estimate ship manoeuvrability in waves.