Study On Energy Dissipation Mechanism Of Twisted Surface Energy Dissipation Pier Under Low Froude Number

The efficient and reliable operation of discharging structures and their energy dissipation and scour prevention facilities is an important guarantee for the safety of hydropower projects.However,in a large number of small hydropower projects,due to their low head,small Fowler number and low energy dissipation efficiency,a large amount of surplus energy of discharging water will cause serious scouring of the downstream riverbed.Therefore,how to effectively solve the problem of energy dissipation and scouring of low Fowler number flow is widely concerned by people in water conservancy circles today.One of the main problems is to study new energy dissipators with high efficiency,which is of great significance for the future development of hydropower projects.Based on the principle of energy dissipation by flip-flop and eddy efficiency,a new type of auxiliary energy dissipator,twisted surface energy dissipator,is proposed on the basis of conventional energy dissipation piers.Hydraulic characteristics of energy dissipation pier are analyzed by combining hydraulic physical model test with three-dimensional numerical simulation.Flow field distribution,velocity variation and vorticity distribution around energy dissipation pier are studied in depth.Aiming at the change of flow field of twisted energy dissipation pier,laser particle velocimeter(PIV)is used to measure the flow field of different parts of pier.The results show that the adjustment of flow field of energy dissipation pier mainly depends on the inclined surface at the top of pier and the twisted surface at both sides.By changing the flow direction smoothly,whirlpools are generated actively in the process of flow and different flow velocities are produced.The shearing friction between the flow and the energy dissipation of the flow is stable,and the rationality of the torsional energy dissipator is demonstrated.Based on the study of the change of flow field of energy dissipation pier,the vorticity field around the pier is further analyzed.The results show that the eddy motion behind the pier is around the pier is further analyzed.The results show that the eddy motion behind the pier is intense,the turbulence intensity of the flow is obviously enhanced,and the energy dissipation in the water body is accelerated after the flow passes through the twisted energy dissipation pier.On the basis of physical model test,the flow field characteristics of energy dissipation pier under test conditions are simulated and calculated by numerical simulation method.The flow field distribution nephogram and velocity vector map around the pier are obtained and compared with the experimental values.The results show that the simulation accuracy is high,and the simulation accuracy can basically reflect the change of flow field caused by the twisted energy dissipation pier,and further to twist.The application of surface energy dissipation pier in engineering provides a reliable basis.The research results show that the design of torsional energy dissipation pier is proposed,which provides a new feasible scheme for low Friedel number dissipation.In the later research,the shape can be further optimized to achieve better effectiveness.