| 泥沙起动概率的高速摄影测量方法 |
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| 引用本文： | 苗蔚,陈启刚,李丹勋,钟强.泥沙起动概率的高速摄影测量方法[J].水科学进展,2015,26(5):698-706. |
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| 作者姓名： | 苗蔚 陈启刚 李丹勋 钟强 |
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| 作者单位： | 1.清华大学水利水电工程系, 北京 100084; |
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| 基金项目： | "十二五"国家科技支撑计划资助项目(2012BAB04B01) |
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| 摘 要： | 为了通过实验测量泥沙起动概率,基于封闭槽道内开展的泥沙起动实验,系统论述了基于高速摄影的起动概率测量方法所涉及的起动概率定义、相机采样频率、图像处理方法、起动比例与运动比例的关系等关键问题.根据泥沙在水流紊动猝发作用下起动的物理机制,定义实测起动概率为单个紊动猝发周期内,从一定面积床面上冲刷外移的泥沙比例.根据推移质运动概念模型,提出高速图片拍摄间隔应小于推移质运动的中间时间尺度,以捕获泥沙的每一次起动.在高速图像处理时,通过连续两帧图片之间的灰度差实现运动比例的无偏差提取.进一步分析表明,运动泥沙可处于起动、止动或滑翔状态,运动比例等于起动比例、止动比例和滑翔比例之和,起动比例与运动比例之比等于两张图片之间的时间间隔除以推移质运动的中间时间尺度.基于上述关键技术,将高速摄影测量方法用于泥沙起动概率的测量,结果表明,临界起动水流条件时,床沙处于少量起动现象,对应的临界起动概率与窦国仁所推导的2.28%接近.
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| 关 键 词： | 泥沙 起动概率 高速摄影 图像处理 猝发 采样频率 |
| 收稿时间： | 2015-03-09 |
Imaging-based measurement of pickup probability for sediment entrainment |
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| MIAO Wei,CHEN Qigang,LI Danxun,ZHONG Qiang.Imaging-based measurement of pickup probability for sediment entrainment[J].Advances in Water Science,2015,26(5):698-706. |
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| Authors: | MIAO Wei CHEN Qigang LI Danxun ZHONG Qiang |
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| Affiliation: | 1.State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China;2.School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China |
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| Abstract: | We present a novel, high-speed imaging method for measuring the pickup probability for sediment entrainment under flowing water. The pickup probability is defined as the proportion of sediment particles entrained from a given bed region during a turbulent bursting period, so the measurement necessitates a least sampling frequency corresponding to the intermediate range of sediment motion. Moving particles are identified by examining the gray difference between two successive images, and the probability for sediment motion is determined by counting the number of particles in motion. The pickup probability equals the probability for sediment motion times the interval between two consecutive images divided by the intermediate temporal range. The method has been successfully applied to the measurement of bed-load transport in closed channel flows. Preliminary results show that the measured pickup probability for sediment entrainment at critical conditions remains at 2.27％, similar to previous results in the literature. |
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| Keywords: | sediment probability for sediment entrainment high-speed photography image processing turbulent burst frame rate |
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