Study On Compensation Measures To Improve The Flow Pattern At The Entrance Of Ship Lock Approach Channel

The navigable flow conditions at the entrance area of the lock approach channel are affected by the discharge regulation of the hub,the boundary conditions of the river channel and the tail water of the power station.In the case of large discharge,the flow pattern near the entrance area will deteriorate,which is not conducive to the navigation of ships.At this time,the water flow conditions near the entrance of the lower approach channel were affected by the sudden expansion of the cross-section,and there appeared strong and wide-range oblique flow and backflow.When the ship enters and exits the approach channel entrance area,the backflow and lateral flow will cause it to drift and twist horizontally,which will cause difficulties for the ship to travel and affect the safety of navigation.Therefore,it is necessary to study the water flow conditions at the entrance of the approach channel under the ship lock.At present,there have been many research results on the engineering improvement measures of the bad flow pattern at the entrance of the approach channel of the ship lock,and they have been successfully applied to various practical projects.However,the research on the improvement effect of non-engineering measures such as the water release dispatching of the hub on the undesirable flow pattern in the entrance area is insufficient,and the longitudinal flow,cross flow and backflow in the entrance area of the downstream approach channel are inseparable from the water discharge of the hub,and the hub should be properly deployed.The operation mode can also improve the navigable water flow conditions in the entrance area.Relying on the second-line shiplock of Xiangjiang River’s Jinweizhou junction,this paper establishes a two-dimensional flow mathematical model that can better simulate complex river boundary conditions,and studies the current supplement measures to improve the flow regime at the entrance of the approach channel of the shiplock by combining with physical model tests.The main research contents and achievements include:(1)Study on the navigable water flow conditions of the entrance area under the conventional design of the discharge opening method.Using a plane two-dimensional mathematical model of water flow,with the help of prototype data,study the water flow characteristics of the entrance area under multi-level flow such as minimum navigable flow,power generation flow,common flood,and maximum navigable flow.It is proposed that the navigation conditions in the downstream entrance area of the second-line ship lock on the Xiangjiang River’s Jinweizhou Junction are the most unfavorable conditions under the conventional design of the discharge opening method.(2)Analysis of the cause of the bad flow pattern near the entrance area.The poor flow pattern near the entrance area of the lower approach channel of the second-line ship lock of Jinweizhou Junction is mainly affected by the large angle between the channel layout and the river flow,the flood discharge method of the pivot,the layout of the ship lock,and the boundary conditions of the pivot building.By clarifying the cause of the unfavorable flow pattern,it can point out the direction for solving the unfavorable navigation conditions near the gate area of the second-line ship lock.(3)Study on the measures and mechanism of side hole flow supplement.By using the method of combining mathematical model and physical model,the influence of the discharge of the side hole(No.22 flood discharge hole near the separation dike of the approach channel of the lock)on the navigable flow conditions in the entrance area is studied without changing the normal discharge opening mode of the Xiangjiang River’s Jweizhou Junction.Based on the requirements of navigable flow conditions in the port area,a reasonable discharge rate of 480m~3/s and a reasonable opening of 4m are proposed.According to the calculation results of the mathematical model,through certain theoretical analysis and mechanism study,the relationship between the discharge of the side hole and the total discharge and the characteristics of the river channel is established,so as to be popularized and applied.(4)Research on other artificial compensation measures.Using Based on the two-dimensional flow mathematical model,the improvement effect of the artificial flow supplement measures on the navigable flow conditions at the entrance area is studied under the condition that the normal discharge and sluice opening mode of Xiangjiang River’s Juanweizhou Junction is not changed basically.Considering the navigable water flow conditions and technical and economic factors in the entrance area,a reasonable compensation flow intensity Q=120m~3/s,compensation flow width B=5m,and embankment head distance L=0m are proposed.