摘要
降雨形成的径流是产生坡面土壤侵蚀的主要动力来源,径流流速是土壤侵蚀模型的重要参数之一。为研究电解质示踪法测量坡面水流流速过程中电解质优势流速和水流流速的关系,本研究利用实验水槽,在坡度4°、8°、12°,流量12、24、48 L/min条件下,于距离电解质注入位置0.3、0.6、0.9、1.2、1.5 m处放置探针测量电解质传递过程,计算不同工况下各测量断面的电解质优势流速。结果表明：流量对电解质优势流速的影响大于坡度对其影响,电解质优势流速随距离增加而增大,采用指数函数拟合计算得到的电解质优势流速随距离的变化过程,得到稳定的电解质优势流速,即水流优势流速,其范围在0.241~0.568 m/s之间。随坡度和流量的增大,水流优势流速均增大。流量对水流优势流速增长的影响大于坡度对其的影响。不同坡度和流量条件下,水流优势流速与平均流速基本一致,二者的比值为1.007,水流优势流速与最大流速的比值为0.774,平均流速与最大流速的比值为0.776,符合坡面薄层水流的流态。结果可为研究坡面薄层水流动力过程提供新的计算方法和参考数据。
[Background] Rainfall runoff is the major dynamic source for hill-slope erosion,runoff velocity is one of the important parameters in soil erosion model. The accurate measurement of shallow water flow velocity is critical in hydrological process. Lei et al. proposed an electrolyte pulse method for measuring the velocity by fitting the solute transport process with time using the least square method and improved the system with a Normal Model and a Sine Model. This laboratory experiments were conducted to determine the relationship between electrolyte peak velocity and water flow peak velocity during the electrolyte transport process and verify the new computational method. [Methods] The experimental devices include a flume,4 m long and 15 cm wide,a solute injector,a data logger for control and data acquisition and a computer with specially designed software for data measurement and storage. The experiments involved three flow rates（ 12,24 and 48 L/min） and three slope gradients（ 4°,8° and12°）. Five sensors were used to measure the electrolyte transport processes at 0. 3 m,0. 6 m,0. 9 m,1. 2 m,and 1. 5 m from the location where the salt solute was injected into the water flow. During each experiment,five complete curves of electrolyte changes with time were recorded,which can be used tocalculate electrolyte peak velocity with the distance from the injection to the measuring sensor and the time used for the peak of the electrolyte to travel through the distance. The leading edge velocities were measured by floating objects method and mean velocities by volumetric method. [Results] The electrolyte peak velocity was between 0. 15 to 0. 54 m/s,increased with distance and tended to stable,and the flow rates caused greater effect on electrolyte peak velocity than slope gradient under different conditions. The steady electrolyte peak velocity,regarded as the water flow peak velocity,were computed through fitting the electrolyte peak velocity at different distances from the salt solution injector with exponential function,ranging from 0. 241 to 0. 568 m/s. The exponential function fitted the electrolyte peak velocities very well for all the experimental conditions. The flow rate had greater effect on flow peak velocity growth rate than that of slope gradient. The water flow peak velocity were 1. 007 times of mean velocity,0. 774 times of leading edge velocity,and mean velocity was 0. 776 times of leading edge velocity. [Conclusions] The flow peak velocity agreed well with leading edge velocity and mean velocity. These demonstrated that the new computational method for measuring shallow water flow velocity was reasonable and valid. The results provide a new method for computing the mean velocity of sheet flow and relevant data for the dynamic process of sheet flow,which will be useful for the investigation of soil erosion.
作者
陈丽燕
雷廷武
啜瑞媛
Chen Liyan Lei Tingwu Chuo Ruiyuan(College of Water Resources and Civil Engineering, China Agricultural University, 100083, Beijing, China Tianjin Lonwin Technology, 300181, Tianjin, China)
出处
《中国水土保持科学》
CSCD
北大核心
2016年第5期130-137,共8页
Science of Soil and Water Conservation
基金
国家自然科学基金重点项目“高海拔寒区融水土壤侵蚀机理与过程模拟研究”(41230746)
关键词
薄层水流
电解质示踪法
流量法
优势流速
平均流速
shallow water flow
electrolyte tracer method
flow method
peak velocity
mean velocity
