Study on the course stability of very large vessels in shallow water using CFD

Abstract

When the large vessels, such as very large container ships and conventional VLCCs, are navigated in shallow water, it is necessary to accurately estimate the course stability as well as the squat of the ship to ensure safety. The purpose of this study is to analyze the course stability characteristics by vessel type, which can evaluate the navigation safety of very large vessels navigating at low speed in shallow water. Numerical simulations were carried out using CFD for KVLCC2 and DTC with respect to depth of water, drift angle, and angular velocity. The maneuvering performance in shallow water were analyzed by estimating the hydrodynamic derivative from the results of the numerical calculations. As the drift angle and angular velocity increased, the magnitudes of sway force and yaw moment became larger. The hydrodynamic derivatives at H/T = 1.2 were very large compared with that at other depths. The course stability at H/T = 1.2 was significant regardless of the type of vessel, and found to be more significant in KVLCC2 compared to DTC. The nonlinear effects such as vortex flow and pressure distribution on the hull were also analyzed through a flow field analysis around the hull.