Study On Hydraulic Characteristics And Type Optimization Of Gradually Broadened Stilling Basin With Slope Behind The Gate

The rational arrangement of water discharge structures is crucial for ensuring the safe and effective operation of water conservancy projects.Stilling basins are one of the most widely used forms of discharge buildings,with strong adaptability,a small scope for flood atomization,and stable flow patterns into the pool.To further improve the performance of stilling basin to adapt to complex engineering conditions and improve the energy dissipation ratio of stilling basin,this paper systematically studied the gradually broadened stilling basin with slope behind the gate.Through theoretical analysis,hydraulic model tests,and numerical simulations,the hydraulic characteristics of the gradually broadened stilling basin with slope are studied,and in view of its unstable jump forward section characteristics,an energy dissipation of hydraulic jump formula based on the equivalent contraction section is proposed to evaluate the hydraulic jump energy dissipation efficiency.Furthermore,a comprehensive performance evaluation method for the stilling basin is developed based on the fuzzy comprehensive evaluation method.The main research results are as follows:(1)This study analyzed the characteristics of the water jump in the gradually broadened stilling basin with slope behind the gate.Considering the difficulty in determining the initial section and water depth of the hydraulic jump in the irregular sloped-type stilling basin,an equivalent contraction section hypothesis is proposed to evaluate the primary water leap dissipation characteristics.Furthermore,this study proposes a formula for calculating the water depth of the tail section of the energy dissipation ridge and an analysis method for the secondary hydraulic jump dissipation principle after the energy dissipation ridge,which helps determine the form of the secondary hydraulic jump articulation after the energy dissipation ridge.(2)The hydraulic model of the gradually broadened stilling basin with slope behind the gate was established.The results show that the hydraulic jump can be effectively controlled by controlling the proportion of the gradual expansion slope section.This can shorten the length of the stilling basin,reduce the bottom velocity of the bottom plate,and decrease the risk of cavitation and cavitation,which ultimately improves the efficiency of dissipation.Within the experimental range,the height of the energy dissipation ridge has a greater influence on the hydraulic characteristics of the basin than the basin’s length.The formula for calculating the energy dissipation rate of the equivalent contraction section can reasonably evaluate the hydraulic characteristics of the stilling basin,and by fine-tuning the height and position of the energy dissipation ridge,the energy dissipation rate of the basin can be increased.(3)In this study,a three-dimensional numerical calculation model of the gradually broadened stilling basin with a slope behind the gate was established and verified through comparison with hydraulic model test results.The model accurately describes the water jump transient process and helps save time and capital costs while ensuring reliable results.The results show that: Ensure that the water jump is fully completed in the dissipation basin and that the inlet flow can be increased appropriately.The small opening during the opening and closing of the gate will not produce an adverse water flow phenomenon.However,it will affect the energy dissipation ratio.It is recommended to open the gate slowly when releasing water for the first time in the basin and then keep the gate fully open when the water level in the pool reaches near the running water level.(4)The fuzzy comprehensive evaluation method of the gradually broadened stilling basin with slope behind the gate was proposed,combined with orthogonal experiments to design and evaluate the experimental group,which increases the dissipation efficiency and the minimum cavitation number of the bottom plate of the gradually broadened stilling basin with slope by 3.31% and 73.33% respectively,which can better meet the energy dissipation and safety requirements.The results obtained using the fuzzy comprehensive evaluation method are consistent with the hydraulic model test and numerical simulation results,which can ensure the accuracy and objectivity of evaluating the comprehensive performance.