Aiming at the problem that uneven flow distribution of lateral branch orifices deteriorates the flow conditions inside the lock chamber of ship locks adopting long-wall corridor lateral branch orifice filling and emptying systems,this paper investigates the coupled effects of lock chamber initial water depth and lateral branch orifice sizes on lock chamber flow characteristics based on existing domestic ship locks.A three-dimensional numerical model is adopted to investigate the effects of initial water depth and lateral branch orifice sizes on three evaluation indices for flow conditions in lock chambers,namely the maximum ship mooring force,free surface fluctuation and average surface flow velocity.Numerical results show that both increasing the initial water depth and reducing the side orifice sizes effectively improve the flow conditions inside the lock chamber.The optimization effect of increasing the initial water depth is superior to that of decreasing lateral branch orifice sizes.Under various lateral branch orifice sizes,lock mooring force optimization efficiency reaches 34%-51% at initial depth h=8.5 m versus h=5.5 m,with milder water fluctuation and surface velocity.Smaller orifices yield better hydraulic indices.The research findings can provide theoretical guidance and technical support for the optimized design of ship locks equipped with this type of filling and emptying system.