Experimental investigation of multi-coupled wave–ship–ship–sloshing interactions

This study investigates the multi-coupling interactions among waves, two parallel surge-free ships, and liquid sloshing through systematic model tests. A dedicated 4DOF (degrees of freedom) motion release mechanism, accommodating surge, heave, roll, and pitch, is designed for the parallel ship configuration. The Korea research institute of ships and ocean engineering Container Ship and David Taylor Model Basin Model 5512 hull forms, each equipped with two liquid cargo tanks, serve as test models. A comprehensive series of experiments is sequentially conducted, encompassing: (i) wave–ship interaction, (ii) wave–ship–sloshing interaction, (iii) wave–ship–ship interaction, and (iv) wave–ship–ship–sloshing interaction. Repeat tests are performed throughout to ensure reliability. Measurements capture the 4DOF motions of both ships, the added resistance, and the sloshing wave elevations within the tanks. Results demonstrate good repeatability, confirming the reliability of the dataset for validating numerical methods. The influences of ship-to-ship interference and sloshing on ship motions, added resistance, and sloshing wave patterns are analyzed and discussed in detail. Crucially, significant coupling effects are identified between the surge degree of freedom and other ship motions for vessels carrying liquid cargo. This finding underscores the necessity of including surge motion in the dynamic analysis of ship responses when sloshing effects are present.