With the rapid development of China’s inland waterway transportation,the increasing number of large-scale ship lock projects with ultra-high heads has made energy dissipater performance a core concern in their design and operation.This study focuses on a four-section outflow cover-plate energy dissipation ship lock characterized by a single-stage head of 40.25 m and chamber dimensions of 265 m × 34 m (length × width).A three-dimensional turbulent flow mathematical model is established,employing the RNG k-ε turbulence model and volume of fluid (VOF) method to simulate hydraulic characteristics during lock filling process.The investigation analyzes three-dimensional flow fields in the chamber,flow distribution through top branch orifices,and energy dissipation mechanisms of cover plates.The results demonstrate that water enters the chamber through top branch orifices as high-velocity jets.During initial filling stages,jet velocities decrease along the flow direction from the longitudinal corridor inlet.When flow rates exceed 100 m3/s,jet velocities progressively increase along the path,with increasingly uneven velocity distribution among top orifices,and the maximum velocity ratio between initial and terminal outflow orifices reaches 1.75.The cover plates effectively reduce jet velocities through obstruction and energy dissipation,with primary energy dissipation concentrated in confined spaces formed between top orifices and cover plates.These findings reveal the regulatory mechanism of cover plate structures on jet flow control and energy dissipation,providing technical references for water conveyance system design in similar ultra-high head and large-scale ship locks.