Evaluation of hydrodynamic performance of a marine train advancing in waves

Marine trains, configured by multiple vessels advancing in a row, provide a promising solution for reducing fuel consumption and enhancing transport efficiency in the maritime industry. As a brand-new concept for marine transportation, there remains a notable gap concerning its hydrodynamic performance. The hydrodynamic interactions and mechanical connections cause their dynamic behaviors to differ significantly from those of traditional vessels. This study aims to investigate the hydrodynamic responses of marine trains composed of multiple carriages under different connection types, providing valuable insights for the design of this joint system to promote its engineering applications. First, an in-house code based on a two-step numerical approach was developed to conduct their hydrodynamic responses, initially solving the hydrodynamic interaction problem, followed by mechanical coupling using the constraint matrix method. The accuracy of this in-house code was thoroughly validated against the published experimental and numerical results. Then, the responses of a marine train configuration with two moving ships were analyzed to examine the effects of various connection types. The results showed that when two ships are either hinged or rigidly connected, the motion response amplitude operators (RAOs) are significantly reduced compared to those of free ships; however, both connection types experience substantial vertical shear forces at the joints. In contrast, the sliding-hinged connection presents a viable solution for marine trains, as it does not increase motion responses while significantly reducing vertical shear forces. Moreover, the responses of a marine train configuration with five moving ships with sliding-hinged connections were analyzed to investigate the effect of advancing speed, joint position, and the gap between ships. The motion RAOs of the vessels increased significantly with rising advancing speed, while remaining relatively insensitive to variations in joint position and the gap between ships.