减速流条件下床面泥沙起动试验研究

Experimental Study on Incipient Motion of Bed Sediment under Decelerating Flow Condition

减速流在工程上称为壅水,为非均匀流的一种流态形式。减速流下的床面泥沙起动研究成果,在水利工程中有着重要的应用价值。通过该条件下的河道开展概化水槽试验,结合天然实测资料以及4家经典的起动流速公式对比分析,结果表明4家经典公式均较适用于水槽试验中的减速流条件,只是在起动粒径的选择上略有差异。根据水槽试验的成果得出选取取样标准为床面泥沙起动标准具有较好的精确性,选取d95作为起动的代表粒径;并验证了减速流条件下泥沙起动大体满足希尔兹曲线;通过功率起动公式的验证,得到无量纲起动功率为0.019 1,可以将其作为床面泥沙起动的标准。

The deceleration flow,called backwater in engineering,is a pattern of non-uniform flow. Research of bed sediment＇s incipient motion under deceleration flow condition is of great application value in water conservancy project.In line with generalized flume experiment and field measured natural flow data,four classic formulae for incipient flow velocity are verified and compared. Results suggest that all the four classic formulae are suitable for deceleration flow condition in flume experiment,yet difference still exists in the selection of particle size. Representative particle size d95 is of good accuracy. Moreover,the incipient motion of sediment under deceleration flow meets the Shields curve in general. According to verification of power incipient motion formula,the dimensionless incipient power is 0.0191,which can be used as the criterion of bed sediment initiation.