Characteristics Of Unsteady Flow Downstream Of Hydropower Station And Itsimpact On Shipping

With the vigorous development of hydropower energy in China,the requirement of stable operation of hydropower station is increasingly high.The power station should not only meet the demand of power grid,but also meet the normal operation and water level regulation in the reservoir area,and at the same time,it may encounter unit failure and cut off the machine.The resulting unsteady flow may cause the water level in the downstream channel to rise and fall steeply,and the velocity is greatly variable,leading to the deterioration of the flow pattern,and adversely affecting the navigation conditions of the river.Therefore,it is necessary to study the unsteady flow in the downstream of the hydropower station.This study with a large water conservancy hub hydropower station and its downstream river as the research object,established the geometric scale of 1:100 normal physical model,and on the basis of the structures,the unsteady flow measurement and control system,for the three groups of live program and 12 groups of peak shaving,flood and peak shaving water combination condition has carried on the physical model test,and in view of the typical working condition of the unsteady flow characteristics are analyzed and discussed.Through this study,the following conclusions are drawn:Firstly,by sorting out the measured data and analyzing the actual scheme,it is found that the water level in the river between cascade power stations is significantly affected by the backwater area of the downstream power station reservoir,and it has spread to the stations from no.5 to no.11.At the same time,the water level and velocity of each downstream station of the hydropower station are all well maintained with the discharge under the power station.Secondly,through the analysis of unsteady flow characteristics under different working conditions,it is found that the water level and velocity of each station along the course all change with the change of discharge flow under the power station.In the process of unsteady flow evolution,the phenomenon of tempering along the course is obvious.Water level and velocity amplitude gradually decrease along the course.At the same time,it is found that the minimum downstream discharge of the power station also determines the magnitude of the water level and velocity amplitude,except that the regulating flow rate amplitude of the power station directly affects the magnitude of the water level and velocity amplitude of the river.In addition,the distribution of section velocity and the influence of compound fault face velocity were analyzed.Then,it is found that the velocity of flow in the downstream of the river is faster,and the velocity of flow is also affected by the initial flow size and flow amplitude.Finally,through the measurement and analysis of the surface flow field of the model channel,it is found that when the initial discharge rate of the power station discharge is 1600m~3/s,the surface velocity of the whole channel is below 3m/s,and the whole section meets the navigable conditions.When the initial discharge from the power station starts to change from 3000m~3/s,part of the river reaches meet navigable conditions.Under the combined and extreme discharge conditions of peak regulation and discharge,the surface velocity is high,changes quickly,and there are many bad flow patterns.Therefore,the downstream river navigation is in danger.