Impact of forward and reverse water capacity difference on open lock operation conditions of Chaohu ship lock

To investigate the influence mechanism of the difference in upstream and downstream water capacity of a ship lock on open lock operation conditions, a two-dimensional hydrodynamic numerical model integrating the ship lock and the upstream and downstream river reaches was developed, with Chaohu ship lock in Anhui Province taken as a case study. The model was used to examine the hydraulic characteristics and conditions of open lock operation of the ship lock, alongside prototype observation experiments. Open lock simulation experiments were conducted on the ship lock at a forward and reverse water level difference of 5–30 cm. The experimental results indicate that because of the forward and reverse water capacity difference, the change in water level difference after stabilization of forward and reverse open lock operations at Chaohu ship lock ranges from 2.7 to 7.1 cm and from 2.8 to 16.6 cm, respectively when the initial water level difference is between 5 and 30 cm. During forward open lock operation, the longitudinal flow velocity ranges from 0.71 to 2.15 m·s^-1, and the transverse flow velocity ranges from 0.11 to 0.48 m·s^-1. During reverse open lock operation, the longitudinal flow velocity ranges from 0.68 to 1.63 m·s^-1, and the transverse flow velocity ranges from 0.09 to 0.30 m·s^-1. For both forward and reverse operations, the flow velocities tend to increase with the increasing water level difference. Nevertheless, the flow velocities during forward open lock operation are significantly higher than those during reverse open lock operation, with the longitudinal and transverse flow velocities during forward operation being 1.04–1.32 times and 1.22–1.60 times those during reverse operation, respectively. Based on a combination of prototype observation, numerical model experiments, and ship lock passage tests, with the maximum transverse and longitudinal flow velocities as discriminant indicators for the safe open lock operation of the ship lock, it is found that the maximum permissible water level difference for forward open lock operation at Chaohu ship lock is 11 cm, while that for reverse open lock operation is 18 cm. This difference in permissible water level differences for open lock operation demonstrates that the forward and reverse water capacity difference has a significant impact on open lock operation conditions.