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

被引:20
作者
Shen JunQi [1 ]
Pan Chong [1 ]
Wang JinJun [1 ]
机构
[1] Beijing Univ Aeronaut & Astronaut, Inst Fluid Mech, Minist Educ, Fluid Mech Key Lab, Beijing 100191, Peoples R China
来源
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY | 2014年 / 57卷 / 07期
基金
中国国家自然科学基金;
关键词
skin friction measurement; particle image velocimetry; single-pixel ensemble correlation; SHEAR-STRESS; BOUNDED FLOWS; MICRO-PIV; HOT-WIRE; RESOLUTION; TURBULENCE; SURFACE;
D O I
10.1007/s11433-014-5462-9
中图分类号
O4 [物理学];
学科分类号
0702 ;
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 (Kahler 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.
引用
收藏
页码:1352 / 1362
页数:11
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