Resistance experiments on ships in a leader-follower formation

The interaction between two ships in a leader-follower formation involves interference by both waves and viscosity, making the phenomenon highly complex. A series of experiments are conducted in this study to measure the total resistance of ships moving individually and in two-ship formations on calm water. The results indicate that the shape of the bow has a more significant impact on the total resistance of single ships than the shape of the stern. Specifically, the total resistance of a single ship with a transom stern is nearly identical to that of a ship with a sharp stern. However, ships with a flat bow exhibit significantly higher total resistance compared to those with a sharp bow. In a two-ship single-file formation, the hydrostatic drag of both the leading and trailing ships is significantly reduced when the gap between the two ships is small. This reduction occurs because the hollow in the water aft the transom stern induced by flow separation is filled by the bow waves of the trailing ship. When the trailing ship is positioned in the divergent wave zone within the wake of the leading ship, wave interference between the two ships becomes the dominant factor influencing the variation in the total resistance of the trailing ship. As the gap between the two ships increases further, the wave interference weakens; however, the trailing ship still experiences a substantial reduction in resistance due to weakened flow separation and bubble drag reduction within the turbulent–bubble mixed flow region.