| 采样频率及样本容量对明渠紊流统计值的影响 |
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| 引用本文： | 王龙,李丹勋,杨胜发,钟强,王兴奎.采样频率及样本容量对明渠紊流统计值的影响[J].水科学进展,2009,20(5):626-631. |
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| 作者姓名： | 王龙 李丹勋 杨胜发 钟强 王兴奎 |
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| 作者单位： | 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; |
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| 基金项目： | 国家自然科学基金资助项目，清华信息科学与技术国家实验室平台部支持 |
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| 摘 要： | 为了研究采样频率和样本容量对明渠紊流统计特征值的影响,利用粒子图像测速技术,对明渠恒定均匀水流的二维流速分布进行测量,获得了包含340535个样本的流场时间序列.对该大容量时间序列进行抽样,得到不同采样频率和容量条件下的一系列子序列.对比分析各子序列的时均流速、紊动强度及雷诺应力的变化特点,发现存在临界的采样频率和样本容量,紊动统计特征参数在临界值以下波动较大,而在临界值以上基本趋于稳定;要满足同一测量精度,时均流速对采样频率和样本容量的要求最低,紊动强度次之,雷诺应力最高.
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| 关 键 词： | 紊流 粒子图像测速仪 采样频率 样本容量 紊动统计特征值 |
| 收稿时间： | 2008-10-29 |
Influence of sampling frequency and sample size on turbulence statistics in open-channel flow measurements |
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| WANG Long,LI Dan-xun,YANG Sheng-fa,ZHONG Qiang,WANG Xing-kui.Influence of sampling frequency and sample size on turbulence statistics in open-channel flow measurements[J].Advances in Water Science,2009,20(5):626-631. |
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| Authors: | WANG Long LI Dan-xun YANG Sheng-fa ZHONG Qiang WANG Xing-kui |
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| Institution: | 1.State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China;2.School of River and Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, China |
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| Abstract: | The influences of sampling frequency and sample size on the accuracy of turbulence measurements are experimen tally investigated.A set of 340535 velocity data are first sampled at a frequency of 600Hz with the particle image velocimetry to measure the turbulent parameters of the flow.A series of statistical samples corresponding to various sampling frequencies and sample sizes are then achieved by extracting data from the original data set.Comparison of the mean velocity,turbulent in tensity,and Reynolds stress obtained from these samples reveals that sampling frequency and sample size both show a threshold value above which the measured turbulence characteristics become relatively stable,and that,to achieve the same level of the experimental accuracy,the required sampling frequencies and sample sizes increase progressively in evaluating mean velocity,turbulence intensity and Reynolds stress. |
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