Numerical investigation of the maneuverability of ships advancing in the non-uniform flow and shallow water areas

Abstract

Sailing attitude would experience many changes when ship entering shallow water, due to the hydrodynamic interaction between ship hull and seabed or riverbed which can be expressed in a significant increase in resistance, sinkage and trim and can engender the safety of ships. A numerical model of ship maneuvering motion that takes account of the shallow water effect is proposed based on the Maneuvering Mathematical Modeling Group (MMG) model. Flow field data solved based on a numerical model of non – uniform flow serves as the basis for calculating hydrodynamic forces of the ship model. Simulations of straightforward, turning and zig-zag motions are performed on a cargo ship using various empirical methods and the fourth-order Runge – Kutta method. Ship trajectories for varying depth-draft ratio, rudder angle and flow velocity are compared, indicating that shallow water effect would increase ship sailing resistance and decrease maneuverability. Result shows that ship maneuverability would be reduced as the depth-draft ratio decrease when ship sailing in shallow water. Application of the model in a typical mountainous river reveals that the model can reasonably simulate the shallow water effect. The study could be a valuable reference for further investigation on shallow water effect, as well as providing guidance on ship maneuvering in shallow waterways.