Unsteady hydrodynamics of a box when entering a lock

The hydrodynamics of ships entering a lock are exceedingly complex. During this process, ships inevitably encounter a sudden
narrowing of the channel and continuous or abrupt variations in water depth. The fluid is displaced and accelerates as
it flows through the gaps between the ship, the lock walls, and the bottom, significantly increasing the risk of collision or
grounding. As a result, the manoeuvrability of ships during lock entry has long been a topic of interest among researchers.
However, beyond this focus, the intricate hydrodynamic phenomena associated with the free surface within the lock during
ship entry have received relatively little attention. This paper aims to explore the causes of these phenomena and analyse
their impacts on ship hydrodynamics, thereby providing further theoretical support for addressing manoeuvrability issues
of ships during lock entry.