To address the issue of excessive transverse flow velocity caused by the northward water diversion from the Huai’an River intake gate on the left side of the downstream approach channel of the Huai’an fourth-line ship lock on the Beijing-Hangzhou Grand Canal,where space for layout is limited,an optimization study on the arrangement of diversion embankments is conducted.Adopting a hydraulic physical model test,an integral physical model with a scale of 1:60 is established for the downstream area of Huai’an ship lock to conduct tests on navigation flow conditions.The results show that:When independent pier-type structures are used for the berthing sections of the fourth-line and second-line locks,water flow tends to pass through the berthing sections,resulting in excessive transverse flow velocity.By adding bottom elevation-gradient perforated baffles at the middle 100 m of the berthing section of the second-line ship lock and the middle-lower 250 m of the fourth-line ship lock to form perforated flow separation dike,water diversion and flow obstruction are achieved,gradually dispersing the flow.Comparative tests on multiple schemes reveal that the transverse flow velocity of the approach channel drops to the specified limit of 0.15 m/s at a porosity of 40%.The proposed bottom-gradient perforated diversion structure effectively resolves the issue of excessive transverse flow in the approach channel and entrance zone,providing valuable insights for the construction and operation of high-grade ship locks under complex working conditions.