非均匀沙卵石推移质输移随机特性研究

使用天然尺度的实验室渠道观测了在恒定流的条件下非均匀卵石床面的推移质运动变化过程,采集到了更高精度、更长时间序列的输沙率变化过程,分析了输沙率统计变化对采样时间的依赖性。实测推移质输沙率的脉动现象十分剧烈,且当采样时间越小时,这种脉动现象越剧烈。来流为4300L/s,采样间隔分别为2、5与10min情况下,输沙率脉动值较平均值分别大约4.8倍、3.3倍与2.7倍;来流为5500L/s,采样间隔分别为2、5与10min情况下,输沙率脉动值较平均值分别大约3.2倍、2.1倍与1.9倍。卵石推移质单宽输沙率的离差系数、无量纲脉动强度以及无量纲极差值均随采样历时与无量纲希尔兹切应力的增大而减小。利用本次试验成果,通过多元线性回归得到的卵石推移质单宽输沙率的离差系数、无量纲脉动强度以及无量纲极差值与采样历时以及无量纲希尔兹切应力的关系式可为工程应用提供参考。

Study on stochastic features of nonuniform gravel bed-load transport

The process of bed-load movement on the non-uniform gravel bed under the condition of steady flow is studied in prototype-scale laboratory channel. The study includes the investigation on the variation of sediment transport rate for different sampling with high accuracy and long-time series, and analysis on the dependence of statistical variation of sediment transport rate on sampling time. The measured bed-load sediment transport rate exhibits significant stochastic features. The shorter the sampling time is, the more intensive the stochastic features will be. With a flow discharge of 4 300L/s, and sampling interval 2min, 5min and 10min, the corresponding fluctuation is about 4.8 times, 3.3 times, and 1.7 times more than the average fluctuation. With a discharge of 5 501L/s, and sampling interval 2min, 5min and 10min, the corresponding fluctuation is about 3.2 times, 2.1 times, and 1.9 times more than the average fluctuation. The dispersion coefficient, the dimensionless turbulence intensity, and the dimensionless ultimate difference of gravel bed-load transport rate per unit width, all decrease with the increase of sampling time and dimensionless shear stress. Using the experiment results, the correlative expression obtained by multiple linear regression based on experimental data can provide reliable basis for engineering application.