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跌坎下游水流和悬沙浓度的分布特性
引用本文:王兴奎,翟大潜,史强,丁忠.跌坎下游水流和悬沙浓度的分布特性[J].应用基础与工程科学学报,1996(4).
作者姓名:王兴奎  翟大潜  史强  丁忠
作者单位:清华大学水电系,美国弗罗里达农机大学和州立大学工学院
摘    要:采用颗粒示踪的方法试验研究了跌坎下游流速和悬沙浓度的时均分布、脉动强度、各点脉动的概率密度分布及相关系数等统计参数.试验结果表明,跌坎下游水流分离,具有稳定的漩涡发展,在Tx>4以后重新接触床面.在其下游,脉动流速的概率密度接近正态分布.颗粒浓度的脉动强度约为浓度均值的一半,浓度脉动的概率密度在跌坎附近明显地偏离正态分布,在较下游时则接近正态分布.

关 键 词:图像处理,流速分布,浓度分布,脉动特性

The Distributions of Velocity and Concentrationin the Downstream of a Backward-facing Step
WANG Xingkui, ZHAI Daqian.The Distributions of Velocity and Concentrationin the Downstream of a Backward-facing Step[J].Journal of Basic Science and Engineering,1996(4).
Authors:WANG Xingkui  ZHAI Daqian
Abstract:The formation of hydraulic drop due to water level rise is a phenomenon frequently encountered in water engineering, and it is important to have a clear understanding of the water flow and sediment motion in such Situations. An experimental study on this problem has been carried out by using the PIV technologyand the results are summarized as follows:1. The separation of flow and formation of stable circulation pattern in thevertical plane took place just downstream of the backward-facing step. Center ofthe circulation gradually reduced its height until it reached the bottom of the flowat the point where Tx>4. The intensity of fluctuating velocity around this area is0. 2, almost two times that in an open channel flow. The probability density distribution of the fluctuating velocity departed from Gaussian distribution in thevicinity of the step, and returned to Gaussian distribution further downstream.The fluctuating velocity has a high degree of auto-correlation, indicating a verystable large scale eddy structure in the flow.2. The vertical distribution of particle concentration is generally uniform andthe intensity of its fluctuation is about half the value of its time average. Its probability density distribution also deviated from Gaussian distribution near the stepand became Gaussian further down stream. The auto-correlation of concentrationfluctuation was very poor, suggesting that particles in the flow were not related toone another in a sure way.
Keywords:image processing  velocity profile  distribution of concentration  turbulence characteristics  
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