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首页> 外文期刊>Experiments in Fluids: Experimental Methods and Their Applications to Fluid Flow >A simple model for the effect of peak-locking on the accuracy of boundary layer turbulence statistics in digital PIV
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A simple model for the effect of peak-locking on the accuracy of boundary layer turbulence statistics in digital PIV

机译：峰值锁定对数字PIV中边界层湍流统计精度影响的简单模型

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摘要

A simple model was constructed to study the effect of peak-locking on the accuracy of particle image velocimetry (PIV) turbulence statistics. A crucial parameter is the ratio between the root-mean-square (rms) velocity and the discretization velocity, which reflects the number of peaks distributed over the velocity probability density functions. When the ratio of the discretization velocity, which is set by the PIV setup parameters, to the rms, given by the flow, is larger than two, the maximum errors introduced in the mean and rms values become significant ( larger than 1%). The errors introduced also depend on the amplitude, or severity, of the peak-locking, and whether the mean displacement corresponds to an integer or a fractional number of pixels. The peak-locking affects the statistical moments of different order in such a way that the errors are phase shifted. The proposed model can be used to predict errors in the turbulence statistics in a laboratory PIV experiment. According to our model predictions, the most significant influence of peak-locking in a boundary layer type of flow is an overall underestimation of the wall-normal rms. Our predictions are in good agreement with our experimental results from turbulent boundary layers and the recent experimental results from a turbulent channel flow by Christensen (Exp Fluids 36: 484 - 497, 2004) for a case of moderate peak-locking.
机译：构建了一个简单的模型来研究峰锁定对粒子图像测速（PIV）湍流统计数据准确性的影响。关键参数是均方根（rms）速度与离散化速度之间的比率，该比率反映了分布在速度概率密度函数上的峰数。当由PIV设置参数设置的离散速度与流量给定的均方根之比大于2时，在平均值和均方根值中引入的最大误差就变得很明显（大于1％）。引入的误差还取决于峰值锁定的幅度或严重性，以及平均位移是对应于像素的整数还是分数。峰值锁定会影响误差的不同阶次，从而使误差发生相移。所提出的模型可用于预测实验室PIV实验中湍流统计数据中的误差。根据我们的模型预测，在边界层类型的流中，峰值锁定的最大影响是对壁法线均方根的整体低估。我们的预测与湍流边界层的实验结果和Christensen的湍流通道流动的最新实验结果非常吻合（Exp Fluids 36：484-497，2004），适用于中等峰值锁定的情况。

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