小底坡长泄洪洞掺气坎体型优化分析
Optimization analysis of aerator shapes in long and mild-slope spillway tunnels
覃月 1王志刚 2李玲 1陈永灿 1刘昭伟1
作者信息
- 1. 清华大学 水圈科学与水利工程全国重点实验室,北京 100084
- 2. 中国水利水电科学研究院水力学研究所,北京 100038
- 折叠
摘要
掺气坎是防止高速水流泄水建筑物发生空蚀破坏的重要结构,然而,在低 Fr 数流动及小底坡条件下易发生空腔回水阻塞通气孔的现象,影响掺气效果,为此,考虑在掺气坎下游设置阻流坡以抑制回溯水流的不利影响.通过理论分析和1:25模型试验,建立了含阻流坡的空腔积水力学模型,研究了阻流坡对小底坡长泄洪洞掺气坎空腔积水情况的影响.研究表明:阻流坡主要通过改变射流冲击角θ2 大小来影响空腔积水情况;对于小底坡泄洪洞,根据阻流坡角度变化对积水域的影响,可将对应空腔状态分为回流满溢段、阻水优化段、净空腔段3个阶段;在试验工况中,综合考虑阻流效果和掺气效果,最佳坡角在阻水优化段出现(21%<γr<41%),此时射流下方形成稳定空腔且水气接触较为充分.本研究可为低Fr数流动下小底坡泄洪洞的掺气坎体型优化提供技术参考.
Abstract
Aerators are critical devices in preventing cavitation damage in high-velocity spillway structures.However,under the conditions of low Froude numbers and mild slopes,cavity backwater is prone to obstruct aeration holes,affecting aeration effectiveness.Therefore,introducing a flow resistance slope downstream of the aerator is considered as a measure to effectively mitigate the adverse effects of backwater.This paper develops a mathematical model for predicting the volume of water accumulation associated with varying flow resistance slopes through theoretical analysis and experimental tests on a 1:25 scale model,and examines the impact of these slopes on cavity water accumulation in mild slope spillways.This study indicates a flow resistance slope affects water accumulation in the cavity through changing the jet nappe impact angle θ 2.For a mild slope spillway,if the effect of the slope change on cavity water accumulation is considered,the cavity conditions can be categorized into three phases:overflow phase,water-blocking optimization phase,and clean cavity phase.In the experimental conditions,when both the blocking and aeration effects are taken into account,the optimal angle occurs in the water-blocking optimization phase(21%<γr<41%),where a stable cavity forms under the jet and the contact between water and air is sufficiently enhanced.This study helps optimize the design of aerators on mild slope spillways under low Froude number conditions.
关键词
掺气坎/小底坡/阻流坡/空腔积水/低Fr数Key words
aerator/slight slope/flow resistance slope/cavity backwater/low Froude number引用本文复制引用
出版年
2025
国家科技期刊平台
NSTL
万方数据