Study On Unsteady Flow In The Approach Channel Of Ship Lock

Filling and emptying of ship lock can form the unsteady flow in approach channel or intermediate channel.The unsteady flow has negative effect on the ship and the ship lock. Previous studies have mostly been based on project needs, the layout of the project type and specific boundary conditions. Due to complexity of the problem and the limitation of methods and scale, systematic and regularity research is shortage. Theoretical analysis, physical model test and numerical calculation methods has been used in this paper, and the relationship between unsteady flow in approach channel and the middle channel when the ship lock filling and emptying, especially the relationship between the scale of approach channel and intermediate channels has been systematically studied.(1) When the length of approach channel is L_n<0.5t_maxc, the value which the maximum reduce of filling water and maximum rising of emptying water increases with the increasing length. When the length of approach channel is L_n<0.5t_maxc, the value which the maximum reduce of filling water and maximum rising of emptying water is basically fixed value.(2) In the design of water depth in approach channel, it should be considered that filling and emptying of lock led to the water depth of approach channel reduce. The empirical formulas were established, which are the formula on water surface reducing, maximum flux and length of approach channel, the formula on water surface rising and maximum discharge, the formula on water surface gradient ratio and maximum discharge rate. It can provide reference for the design of approach channel.(3) Under the condition of different lock chamber scales of same ship lock grade, the filling discharge of approach channel were different, there were great difference to hydraulic conditions and mooring conditions of approach channel.So in the design for corss sections of approach channel, it should be considered that the width variation of lock chamber lead to the hydraulic fators of approach channel changing.(4) The different period wave in intermediate channel of ship lock is composed of progressive wave (positive wave) or discharging wave (negative wave) and reflected wave and oscillatory wave.The fluctuate period has relation to the length of channel and water depth, finally, the oscillatory wave which wave node is in the middle of ship lock formation.(5) The height of oscillatory waves can reach the biggest value when the length of intermediate channel is the half of wave length of progressive wave or discharging wave, that is L_n<0.5t_maxc, this length of channel should be avoided in design. Engineering measures or operational measures can be adopted to change the wave length of progressive (positive wave) or discharging wave (negative wave) to improve the current condition in intermediate channel when changing the length of channel is difficult.(6) The empirical formulas ofâ…£grade intermediate channel on wave elements and unit width discharge in channel were established. When the scales of channel were known, the filling and emptying discharge of shiplock can be confirmed by the method of interpolation and extension according to the relation of unit width discharge and flow condition.Of course, the scales of channel can be calculated according to filling and emptying discharge.(7) The wave height gradually reduces during the course of positive wave propagating and gradient ratio in front of wave increases.To some extent, the shape in front of the wave is nomore stable, a series of short period wave will appeared.Large intension short wave has negative effect on navigation of ship in intermediate channel.