高分辨率粒子示踪测速技术在光滑明渠紊流黏性底层测量中的应用  

High resolution PTV system and its application in the measurement in viscous sub layer in smooth open channel flow

作　　者：钟强[1] 王兴奎[1] 苗蔚[1] 李丹勋[1] 

机构地区：[1]清华大学水沙科学与水利水电工程国家重点实验室,北京100084

出　　处：《水利学报》2014年第5期513-520,共8页Journal of Hydraulic Engineering

基　　金：国家自然科学基金项目(51127006);十二五科技支撑项目(2012BAB04B01)

摘　　要：在光滑明渠紊动水流的研究中,黏性底层具有重要的作用,壁面剪切应力与涡量均源于此流区。由于充分发展明渠紊流的黏性底层的物理尺度在0.1 mm量级,常规方法难以实际测量该区内的速度分布。本文构建了测量黏性底层的高分辨率HR-PTV与测量全流区的普通PIV的耦合测量系统,对光滑明渠紊流黏性底层的流动特性进行了研究。HR-PTV系统采用阈值递增法、灰度截断、椭圆度与充实度指标等方法进行图像处理得到清晰的粒子图像;使用匹配几率法对粒子坐标进行匹配,计算粒子速度。得到了明渠紊流黏性底层(0.3 mm以内)的平均流速、紊动强度、偏态系数和峰度系数的垂线分布。从拟合的平均流速分布得出摩阻流速u*,结果与牛顿流体本构方程一致;黏性底层与全流区的时均流速、紊动强度和雷诺应力均能用拟合所得的u*合理无量纲化,并能光滑连接,表明由此得出的u*适用于全流区。将明渠紊流的各种分布与封闭槽道流DNS数据进行对比,验证了HR-PTV在黏性底层所得各阶速度矩的准确性。Viscous sublayer has an important role in open channel flow, and shear stress and vorticity are both derived from this area. Due to its physical dimensions is in the order of 0.1 mm in fully developed turbulence flow, common measurement methods are difficult to observe viscous sub layer. This paper illustrates a High-Resolution PTV coupled PIV system built for measuring the inner and outer layer of open channel flow. The threshold iteration increasing method,gray truncation method,elliptical indicator and filling indicator are used for High-Resolution PTV image processing. Probability matching method is used for matching the particles and calculating the velocities. The mean velocity, turbulence intensity, skewness and kurtosis distribution in viscous sublayer are got in open channel flows. The friction velocities were got by fitting the mean velocity distribution in viscous sublayer, and the results are consistent with the Newtonian fluid constitutive equation. The mean velocity, turbulence intensity and Reynolds stress of inner and outer layer can all be converted into reasonable dimensionless by the friction velocity from fitting the mean velocity distribution in viscous sublayer, and data in the share region between HR-PTV and PIV can connect smoothly. Various distribution of open channel flows were compared with the data from direct numerical simulations in channel flow to verify the results.

关 键 词：黏性底层 流速分布 偏态 峰度 

分 类 号：O357.54[理学—流体力学] TV131.21[理学—力学]