非恒定流作用下砾石推移质输移特性试验研究

摘要

Based on the change rate of water depth and discharge, dimensionless parameter P reflecting the unsteadiness of unsteady flow has been proposed. The gravel bed-load transport in unsteady flow was ex-perimentally investigated with the synchronous test system of unsteady flow sediment transport. Test data analysis shows that bed-load transport under unsteady flow displays randomicity, intermittency and parox-ysm. Unsteadiness has effects on pulsation of peak for sediment transport rate. In the case of unsteady flow with strong unsteadiness,i.e. P>0.32,if samples of sediment transport rate are less than 20,the outcome will be deviated. The variation of sediment transport rate under unsteady flow does not synchronize with flow condition,and also relates to unsteadiness. When P>0.32,the peak of sediment transport rate usually lags behind the peak of flow velocity;while P<0.32, the peak of sediment transport rate perhaps occurs before the peak of flow velocity. Bed-load average transport rate (or bed-load yield) in unsteady flow is re-lated to discharge per unit width (or runoff) and unsteadiness parameter P,and increases as P strengthens.%　　基于水深与流量的变化率提出了反映水流非恒定强度的无量纲参数P。利用水槽非恒定流输沙同步测试系统试验研究了非恒定流作用下砾石推移质的输移特性。试验资料分析表明，非恒定流作用下的砾石推移质输移具有明显的随机性、间歇性与阵发性。水流的非恒定性对输沙率峰值的脉动性有影响，对P＞0.32的强非恒定流而言，若输沙率样本数少于20，将会给输沙率结果带来较大的偏差。非恒定流作用下输沙率与水流要素变化具有不同步性，并与水流非恒定强度有关。P＞0.32时，输沙率峰值一般滞后于流速峰值；当P＜0.32时，可能出现输沙率峰值先于流速峰值的现象。非恒定流作用下砾石推移质平均单宽输沙率（或输沙量）与单宽流量（或径流量）、非恒定强度参数P有关，随P的增强而加大。