紊流消能与泥沙制紊分析

Analysis on Energy Dissipation by Turbulence and Turbulence Prevention by Sediments

在一次洪水过程中，各时点含沙量随水流紊动及摩阻比降而正变，紊流消能规律占主导；而对于一个洪水过程整体，间歇性的泥沙与水流的滑脱影响积累起来，显示出泥沙制紊作用．在河流多次洪水记录中，取洪水期平均流量大致相等的儿次洪水相比较，可看出泥沙制紊作用并与试验室水槽内多次稳定流实验结果一致：洪水期平均含沙量较大的洪水，其加权平均流速较大，而加权平均摩阻比降较小．反之亦然．文中用大量实际资料对紊流消能和泥沙制紊进行了论证．

The flood process is analyzed in totality and in time steps respectively. It was found that at each time step the hydrological elements of a flood process, such as sediment contents, turbulent velocity and resistance slope, vary in direct proportion with each other, which shows that energy dissipation by turbulence is dominant. While for the whole flood process the turbulence prevention by sediments appears to be a controlling factor due to the accumulative effect of intermittent slipping of sediments from flow. Comparing those flood processes with similar dis- charges in the long-term flood records, the phenomenon of sediments preventing turbulence is also found. The fea- tures is found to be in accordance with the results of steady flow in laboratory flume, i. e., for the flood with larger sediment contents in flood season, its weighted mean velocity is also larger but its weighted mean resistant slope is smaller. In this paper, both features of energy dissipation by turbulence and turbulence prevention by sediments are demonstrated by measured data in Yangtze River and Yellow River.