Model Test Study On The Energy Dissipation Effect Of Double-layer Side Ports On The In-chamber Long Culvert Of A Ship Lock

As an important form of the dispersive filling/emptying system for locks,the inchamber long culvert with side ports has been widely used in medium-and high-head lock projects.However,this type of the filling/emptying system is difficult to be used in high-head or ultra-high head locks.In view of this,researchers have done a lot of work on how to improve the applied head of this filling/emptying system,and found that the vertical double-layered side port arrangement form can obtain better energy dissipation effect.However,the relevant research results obtained are still at the level of the hydraulic characteristics of the lock water transfer,and no assessment of the lock chamber ship berthing conditions has been carried out.Therefore,this paper adopts a combination of physical and mathematical models to compare and analyze the mooring conditions of single and double-layer side port arrangements in order to comprehensively evaluate the energy dissipation effect of double-layer side port in the bottom of the lock chamber.The main research results obtained are listed as follows:(1)Based on the physical model of the filling/emptying system with a scale of1:25,the filling process of the double side port arrangement schemes under different head conditions was tested respectively,and through comparative analysis,it was found that the energy dissipation effect of the double-layer side port arrangement was significantly better than that of the single-layer side port arrangement under the same conditions.(2)By analyzing the shortest opening time of the valve under the criteria of ship berthing,it is found that under the same conditions,the shortest opening time of the valve of the double-layer port arrangement is significantly faster than that of the single-layer arrangement,and the corresponding water filling time is smaller than that of the single-layer arrangement.(3)Tests were conducted on the filling and emptying process at different locations of the locks,and it was found that the upper part of the lock chamber had the worst mooring conditions during the filling process,which was consistent with the water surface slope drop characteristics derived from the simulations using the 3D mathematical model.(4)Based on the three-dimensional numerical simulation results,a comparative analysis of the longitudinal and transverse water surface ratio drop in two typical moments during the filling process of the two side port layout schemes was carried out,and it was found that the double-layer side port scheme was better than the single-layer side port scheme,which was consistent with the result of the physical model test.(5)By analyzing the turbulent energy and flow field distribution during the filling process of the two schemes,the energy dissipation mechanism of the two layout schemes was revealed.The energy dissipation mechanism of the double-layer side port scheme is as follows:(1)the side port suddenly shrinks and expands to generate vortex for energy dissipation;(2)the side port jet collides with the side wall to form vortex for energy dissipation in the open channel;(3)the upper and lower side port water body diffusion after squeezing and mixing for energy dissipation;(4)the water body rises and mixes energy dissipation with each other.Single layer side port scheme energy dissipation mechanism is:(1)side port sudden shrinkage sudden expansion to generate vortex for energy dissipation;(2)side port jet and the side wall collision in the open channel to form a vortex for energy dissipation;(3)water body rising mutual mixing for energy dissipation.