矩形明渠掺气水深和底掺气浓度计算公式探讨  

Discussion on Calculation Formula for Aerated Depth and Bottom Air Concentration of Rectangular Open Channel Flows

作　　者：李勇泉 蔡芳 LI Yong-quan;CAI Fang(Basin Hub Operation Management Center of China Three Gorges Group Co.,Ltd.,Yichang 443134,China;Changjiang Survey,Planning,Design and Research Co.,Ltd.,Wuhan 430010,China)

机构地区：[1]中国长江三峡集团有限公司流域枢纽运行管理中心,湖北宜昌443134 [2]长江勘测规划设计研究有限责任公司,湖北武汉430010

出　　处：《水电能源科学》2022年第7期151-155,共5页Water Resources and Power

摘　　要：掺气水深直接决定泄水建筑物的边墙高度,底掺气浓度对空蚀预防有重要作用。我国现行的规范中对纯水深、掺气水深的定义较为模糊,且断面平均掺气量估算公式的适用范围和准确性也不明确。为此,总结了多个研究成果,对明渠水气两相流进行了分区,明确了通过体积分数等值线定义掺气水深的方法,分别针对均匀流区、掺气衰减区和掺气发展区总结了断面平均和底掺气浓度的估算方法。同时,分析了掺气对壁面阻力的影响,提出了掺气水流壁面阻力的修正公式,并对比了若干掺气水深计算公式的准确性。研究表明,壁面阻力修正系数和断面平均及底掺气浓度呈现线性关系;对于均匀流的掺气水深,霍尔公式和斯里斯基公式的计算结果与试验值相符较好,在弗劳德数小于20时王世夏公式的准确性最高;溢洪道规范公式和王俊勇公式的计算结果明显偏小,而王世夏公式在高弗劳德数下的计算结果则显著偏大。研究成果可供工程设计参考。Aerated flow depth directly determines the height of spillway side wall.The bottom air concentration plays an important role in preventing hydraulic structures from potential cavitation erosion.However,the definitions of pure water and aerated flow depth in the existing design criterion remain vague.Moreover,the applicable scope and accuracy of the existing formula for calculating the cross-sectional average air concentration is also still unclear.Several classical literatures were summarized and thereby a partitioning method for air-water two-phase flow was put forward and then the aerated flow depth was defined quantitatively by the contour line of gas volume fraction,the corresponding calculation method of pure water depth was introduced.The calculation methods of the cross-sectional average air concentration and near-wall air concentration were summarized for the uniform flow,the aeration decreasing and the aeration developing region,respectively.The effects of aeration on the wall resistance and the accuracy of the calculate formulas for aerated flow depth were compared and analyzed.It was found that the wall resistance correction factor is almost linearly related to the near-wall and cross-sectional average air concentration.The Hall formula and Slyski formula were relatively reliable,the Wang Shixia formula features the highest accuracy when the Froude number is lower than 20.However,the calculated cross sectional average air concentration from the Spillway Design Specification and Wang Junyong formula are lower,and that from Wang Shixia formula is larger under large Froude numbers than the measured data.This paper is instructive for relative project design.

关 键 词：掺气水深 底掺气浓度 气液两相流 壁面阻力 掺气衰减速率 

分 类 号：TV135.2[水利工程—水力学及河流动力学]