Numerical Simulation Of The Influence Of Dropping Water Level Downstream On Underflow Energy Dissipation And Erosion Prevention In Sluices

There are many reasons for the destruction of energy dissipation and erosion prevention facilities.For example,the energy dissipation of low Froude number in the stilling basin of sluices in the plain area has caused the energy dissipation to be insufficient.So scholars have proposed to build assistance in the stilling pool to increase energy consumption and improve the anti-scour stat;irrational gates opening will also have an adverse impact on the energy dissipation and erosion prevention of sluices.The broken energy dissipation and anti-scour facilities caused by dropping water level downstream has drawn attention,but the sluices management department is almost incapable of dealing well with it.And the downstream water level reduction is a slow process,the impacts are like "warm boiled frogs" and people are gradually paralyzed.The average annual decline of the water level may be a few centimeters or a few tenths of it,which seems to change little compared with the previous years.No obvious impact or damage can be seen at one time,and the sluices won’t be able to operate in the short term.In that case,the downstream water level decline is often overlooked by sluice managers.When the water level drops to a certain "critical value",it will be harmful to the energy dissipation and anti-scour facilities which is not easy to be discovered at the beginning.When the dropping of downstream water level exceeds the "critical value",the speed of destruction will accelerate and the difficulty of repairing the facilities becomes bigger.Therefore finding this "critical value" is crucial for the operation and management of the sluices.This paper firstly summarizes the design and operation of bottom flow energy dissipation and anti-scour facilities,the problems in its operation and the main influencing factors.It explores the conditions and causes of downstream water level decline of sluice and uses the engineering project to analyze changing process of downstream water level,as well as its impact on energy dissipation and anti-scour facilities.Secondly,theoretically analyzing the impacts of downstream water level decline on energy dissipation and erosion prevention of sluices and using Flow-3 d to model the new project of Renhe Sluice,Liuxi River in Guangzhou.The analysis show that under the same range of water level decline,the small flow working conditions are more likely to be affected by the drop of downstream water level than the large flow working conditions while the gates are fully opened.At the same time,far-reaching water leaps occur in the stilling basin while the flow velocity in the apron is bigger than the allowed number,so we can get the "critical value" of the downstream water level decline.Finally,take measures on the comprehensive prevention and control of this problem,such as taking the downstream water level decline into consideration previously when design the stilling pool,manage to improve or eliminate the decline of downstream water level and improve the energy dissipation and enhance the quality of erosion prevention.In short,the numerical simulation method can help explore the critical value of the destruction of energy dissipation and anti-scour facilities.It is feasible to use the critical value to achieve early warning.