Study of shallow-water effects on ship maneuverability using free-running model tests

Abstract

In this study, we conducted turning tests with rudder angles ±35∘ and ±20∘/20∘ zig-zag maneuver tests in deep and shallow water using a model of a 3,600 TEU container ship called KCS. Through the comparison of these test results with the free-running test results of three other ships, the shallow-water effect on the maneuverability was investigated. The shallow-water effects obtained during the turning and zig-zag maneuvers are as follows: Turning: The advance (AD) decreases slightly when the water depth-to-ship draft ratio (h/d) is approximately 2.0 and increases significantly as the water depth decreases. The tactical diameter (DT) (up to h/d=2.0) is approximately the same as that in deep water and becomes significantly larger when h/d becomes smaller than 2.0. Thus, there is a slight difference in the appearance of the shallow-water effects in AD and DT. Zig-zag maneuvers: The overshoot angle increases slightly near h/d=2.0 compared with that in deep water and becomes significantly smaller as the water depth becomes shallower. The forward distance (l20), until reaching the heading +20∘/-20∘ after steering, was approximately the same as that in deep water or decreased slightly, until approximately h/d=2.0. Furthermore, it increased as the water depth decreased. This is because the course stability of the ship deteriorated at approximately h/d=2.0.