Study On Energy Dissipation Characteristics Of Stepped Energy Dissipator In Spillway

Spillway is a very common structure in water conservancy project,which plays an important role in releasing excess flood and ensuring the safety of downstream structures.Previous studies have shown that the energy dissipation rate of smooth spillway is only about 10%,and the efficiency of stepped spillway can reach more than 90%.In terms of energy dissipation rate,stepped spillway has obvious advantages.Based on the stepped energy dissipation project of a park spillway in Shanxi Province,this paper studies the energy dissipation characteristics of stepped spillway under different discharge by combining physical model test and numerical simulation,and obtains the following conclusions:(1)The velocity of stepped spillway decreases gradually from top to bottom in the vertical direction of flow,but its change law is not exactly the same as that of smooth spillway;along the direction of flow,the velocity first increases and then decreases,and finally tends to be stable;there is obvious clockwise vortex in the concave corner of the step,and the velocity gradually increases from the center of the vortex to the surrounding;the velocity from the outside of the step to the platform The corner of the step decreases gradually,which indicates that the energy loss occurs in the corner of the step,and part of the loss comes from the vortex.(2)There is negative pressure on the vertical face of the step,and the negative pressure on the vertical face of the step is in the middle and upper part of the vertical face of the step(the negative pressure area begins to enter at about 0.8 times of the vertical height of the step);the maximum value of the bottom plate pressure of each step appears in the middle and lower part of the bottom face of the step(about 0.8-0.9 times of the horizontal length of the step),and the bottom plate pressure of the step flood chute increases with the flow as a whole There is negative pressure at the bottom of the step under the five flow rates,and the maximum value of the absolute negative pressure at the bottom of the step increases with the flow rate.(3)In stepped spillway,it is easier to form falling water flow under low head and sliding water flow under high head;the cavity formed by water flow on the step is closer to the bottom of water flow;the length of jet water increases with the increase of flow;the length of water jump increases with the increase of flow after the water leaves the stage to the horizontal section of the spillway.(4)At the first end of the step,the water surface profile first decreases,then increases,and finally tends to be stable,but on the whole,it fluctuates along the course.The larger the flow is,the more obvious the water surface profile fluctuates.Under the same flow,the water surface profile fluctuation of the last three steps is stronger than that of the first three steps.(5)In this study,the energy dissipation rate of step type energy dissipator decreases with the increase of flow rate,and the maximum is over 70%.The turbulent kinetic energy at the end of the stage reaches the maximum,and the turbulence intensity reaches the maximum.The research results of this paper provide a theoretical basis for the application of stepped energy dissipator in a park spillway project in Shanxi Province and similar projects.