Simulation Of Water And Sediment Characteristics In The Gate Area Of Pilot Crossing In Curved Reach

With the continuous advancement and development of my country’s economy,more and more water conservancy projects are under construction,and inland water transportation has also achieved certain development.The number of berths,transportation capacity,freight volume and cargo turnover of ports have maintained stable growth.As an important part of the comprehensive transportation system,inland water transportation will still occupy an indispensable position in the comprehensive transportation system of the river basin.Whether ships(teams)can enter and leave the lock safely,Convenience and speed are closely related to the water flow conditions at the entrance of the approach channel.That is,it is required that the longitudinal and transverse velocity in the gate area of the pilot crossing should not be too large,and complex flow patterns should not appear,such as bubble vortex,high-intensity vortex,reflux,etc.Therefore,it is very necessary to study the water and sediment characteristics of the gate area of the pilot crossing to ensure the safety of ship navigation.Based on the practical problems of the approach channel entrance area of guotan navigation hub,In this paper,the combination of numerical simulation and physical model test is used to study and analyze the water and sand properties of the inlet area of the upstream and downstream approach channels under different working conditions.The results are as follows:(1)Through analysis and comparison,the hydraulic model test value and the numerical simulation simulation value are verified.The simulation value of the mathematical model is basically consistent with the test value of the model test,which can better simulate the water and sand conditions in the approach gate area.(2)The mathematical model of the approach course was established with Mike21,and the water flow change law in the gate area of the pilot channel is obtained.The main stream of the river is diverted in front of the gate area of the upstream approach channel,resulting in backflow vortex,sliding slightly to the left bank,and moving forward to the discharge outlet of the sluice with the main stream.When the discharge of the sluice is consistent,The section velocity in the gate area of the pilot channel increases with the increase of flow,and the return vortex displacement increases with the increase of the included angle between the main stream and the axis of the approach channel.(3)According to scheme 1 and scheme 2,compared with the middle four holes,the upstream and downstream backflow vortex range is small,the backflow velocity is small,the oblique flow effect is weak,the flow fluctuation range in the portal area is small,and the backflow vortex position is far from the portal area.It can be seen from scheme 3 and 4 that compared with the right hole,the range of upstream and downstream backflow vortex is larger,the oblique flow effect is obvious,the backflow velocity is large,the distance from the gate area is close,and the boundary gyration area of the downstream pilot crossing gate area is larger.Therefore,when controlling the gate dispatching mode,scheme 1 is better than scheme 2,and scheme3 is second than scheme 4.Through the combination of gate opening and dispatching,with the increase of the included angle between the gate area of the pilot crossing and the main stream of the river,the backflow effect of the gate area of the pilot crossing gradually decreases,resulting in the decrease of the transverse velocity in the approach channel,the oblique flow effect(weakening),and the flow pattern tends to be relatively stable,meeting the navigable flow standard.(4)The influence of the opening and closing of the dredging sluice on the change of the scour and silting depth in the upstream diversion sluice area is discussed.The results show that when the upstream inflow is consistent,the scouring and silting effect of opening the desilting gate is better than that of closing the desilting gate.Through the desilting gate,the sediment deposition in the gate area of the approach channel can be reduced.When the discharge of the upstream sluice is consistent,the regulation mode of the sediment discharge sluice and the sluice is combined,that is,when the included angle between the main stream of the river and the entrance area of the approach channel becomes larger,the scouring and silting effect will be enhanced.(5)When the discharge of the control gate is consistent,that is,open the four hole gate.With the increase of the flow,compared with scheme 2,scheme 1 has a smaller range of backflow area in the gate area of scheme 1,the maximum vertical and horizontal flow velocity is relatively small,and the flow state is stable.Compared with scheme 3,the difference of the maximum transverse velocity extreme value in the upstream and downstream portal area of scheme 4 is small,but the range and velocity of the reflux area are small.The reflux velocity meets the inland navigation standards,and the water flow tends to be gentle.Therefore,by controlling the dispatching mode,the backflow and oblique flow effects can be effectively weakened and the water flow conditions in the portal area of the approach channel can be improved.(6)Through the analysis of the measured data of the model test,the section velocity distribution and sediment erosion and deposition distribution in the portal area of the approach channel are compared.The results show that the change of operation mode in the portal area of the upstream and downstream approach channel is better than the comparison scheme(scheme 1 is better than 2 and scheme 4 is better than 3),which verifies the feasibility of the model test to study the water and sediment characteristics,and provides a reference for the design of similar hubs in practical projects.