Accurate measurement of wall skin friction by single-pixel ensemble correlation

查看全文 作　　者：SHEN [1]JunQi;PAN [1]Chong;WANG [1]JinJun

机构地区：[1]Fluid Mechanics Key Laboratory of Ministry of Education, Institute of Fluid Mechanics, Beijing University of Aeronautics and Astronautics

出　　处：《Science China(Physics,Mechanics & Astronomy)》索引2014年第57卷第7期,共11页

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.11327202 and 11372001) 摘　　要：The present work deals with accurately estimating wall-skin friction from near-wall mean velocity by means of PIV measurement.The estimation accuracy relies on the spatial resolution and the precision of the resolved velocity profile inside the viscous sublayer,which is a big challenge for conventional window-based correlation method(K?hler C J,et al.Exp Fluids,2012,52:1641–1656).With the help of single-pixel ensemble correlation,the ensemble-averaged velocity vector can be resolved at significant spatial resolution,thus improving the measurement accuracy.To demonstrate the feasibility of this single-pixel ensemble correlation method,we first study the velocity estimation precision in a case of steady near-wall flow.Synthetic particle images are used to investigate the effect of different image parameters.It is found that the velocity RMS-uncertainty level of the single-pixel ensemble correlation method can be equivalent to the conventional window correlation method once the effective particle number used for the ensemble correlation is large enough.Furthermore,a canonical turbulent boundary layer is synthetically simulated based on velocity statistics resolved by previous Direct Numerical Simulation(DNS)work(Schlatter P,et al.J Fluid Mech,2010,659:116–126).The relative error of wall skin friction coefficient is shown to be one-order smaller than that of the window correlation method.And the optimization strategy to further minimize the measurement uncertainty is discussed in the last part. 关键词：像素精确测量集成摩阻力直接数值模拟表面摩擦系数平均速度空间分辨率

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Accurate measurement of wall skin friction by single-pixel ensemble correlation

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