Research On Energy Dissipation Pattern Of Gravity Dam In High Water Downstream

The energy dissipating facility is a building that is widely used in the construction of water conservancy projects.Along with the development of the water conservancy industry,there are more and more problems to be solved when selecting energy-dissipating buildings.For example,when the downstream water level is high,the water discharge building is subjected to the support of the downstream water level,resulting in a high-water level in the stilling basin.Among the three conventional energy dissipating types currently used,which one is suitable for the gravity dam with higher downstream water level,it is necessary to test various energy dissipating structures.This has profound implications for ensuring dam discharge safety and improving economic efficiency.This thesis is based on Flow-3D software to simulate two three-dimensional models of energy dissipation by hydraulic jump and surface flow energy dissipation.Study the hydraulic characteristics of the two energy dissipation schemes and compare them with the data of the hydraulic model test.Then,the energy dissipation suitable for the gravity dam with higher downstream water level is selected by integrating the pressure,flow velocity and energy dissipation rate of the bottom plate of the stilling basin.Finally,the optimal design of the length and depth of the tilling basin is selected for the selected energy dissipation type.The main contents and results of this thesis are as follows:（1）The selection of energy dissipation type and test conditions based on the actual engineering work.According to the impact performance of the underlying bedrock downstream of the dam and the higher flood level at the downstream of flood discharge（the downstream water level in 30 years has been higher than the dome）,determining that it is not advisable to use energy dissipation of ski-jump type.Therefore,two schemes of energy dissipation by hydraulic jump and surface flow energy dissipation are proposed.Through the collected data of Dashiqiao Reservoir and the experimental data of hydraulic model,the research conditions（9 kinds）and research contents（Flow regime,bottom plate pressure,flow velocity distribution and energy dissipation rate）of this thesis are determined.（2）Through the hydraulic calculation and numerical theory research of the energy dissipating type,the most unfavorable working condition of energy dissipation is obtained:the upstream water level is 251m,and the discharge flow rate is Q_p=3.33%=963m³/s（subject to the downstream water level）.Based on the hydraulic calculation manual,calculate the flow coefficient under various working conditions,the water depth of the contracted section and the most unfavorable working conditions corresponding to the two energy dissipating types,and design the dimensions of different energy dissipating types.Then based on the numerical simulation theory,considering the characteristics of Flow-3D software,the calculation range,turbulence model,discrete method,mesh size,boundary conditions and other parameters of the project are drawn up.（3）Based on the results of the three-dimensional numerical simulation of two energy dissipations,it is proposed that the energy dissipation by hydraulic jump is more suitable for the downstream high-water level and optimize the reasonable design parameters.The flow characteristics（the surface flow pattern,floor pressure,outlet velocity and energy dissipation rate）of the energy dissipation by hydraulic jump and the surface flow energy dissipation under nine working conditions with or without the influence of the downstream water are studied.Then compare the test results of the hydraulic model,select the energy dissipation type suitable for the project,and finally optimize the selected energy dissipator type in the pool length and pool depth.Through the results of hydraulic model,software simulation data and practical application of the project,it is recommended to select the energy dissipation by hydraulic jump in the gravity dam with higher downstream water level.