基于床面形态的泥沙输移模式及其在黄河下游的应用

Bedform-dependent sediment transport model and its application in the Lower Yellow River

冲积河流系统中,水流在不规则床面上产生的漩涡对泥沙悬浮效率影响很大。基于漩涡流的运动特征及床面形态控制数m,本文研究了水流阻力与床面形态运动之间的关系。同时,在Bagnold泥沙悬浮效率(sηl)概念的基础上,提出了床沙质输沙能力公式,对其中的sηlC*进行了深入研究,建立的sηlC*与1/m的关系,能够反映床面形态由低能态到高能态区的发展过程。研究提出的输沙公式,经黄河下游调水调沙试验等实测资料验证表明,计算结果与实测值特别是相对平衡条件下的实测值吻合较好。在输沙能力公式研究中引入反映床面形态控制参数是一种新的尝试,该方法在研究中显示出较大的发展潜力。

Bed irregularities in shallow alluvial systems induce flow separation and vorticity, which can significantly influence sediment suspension efficiency. Based on the vortex-shedding activity and a control factor m, the link between resistance-to-flow and bedform development is studied. Using Bagnold＇s resuspension efficiency concept （ηsl ） ,we derive a transport capacity formula for bed-material load. It is suggested that ηslC. in the formula can be deduced from the knowledge of m. In particular, the plot of ηslC. against 1/m appropriately reflects the sequence of bedform development from the lower-to the upper-alluvial regime. The sediment concentrations predicted by the formula in which m has been introduced agree fairly well with the observed during LYR ＇silt-flushing experiment＇, especially those close to sediment-transfer equilibrium conditions in the considered reach. The use of an explicit bedform descriptor in a transport capacity formula is novel and seems very promising.