摘要
泥沙起动是河流动力学基础理论中最基本的问题之一.从非均匀沙起动的特点出发,研究了泥沙颗粒起动的内在机理及水力、泥沙因素在泥沙起动中的作用.通过对瞬时作用流速及起动标准、泥沙颗粒在床面的相对暴露度、附加质量力等问题的分析及其表达式的引入,使泥沙起动在理论上进一步完善.采用泥沙颗粒沿床面滚动的模式,推得了非均匀沙起动临界无因次切应力公式.该公式包含了与水流脉动及泥沙颗粒相对暴露度相关的系数.对公式中的系数进行了理论分析,并采用实测资料进行了检验,证明了公式的合理性.
Incipient motion of sediment is one of the most fundamental problems in the theory of river dynamics and remains a challeng due to its un steady and random characteristics in the process. In this paper, the mechanism of initial motion, the effects of flow and sediment factors are studied for non-uniform sediment. The theory of threshold status of sediment is analyzed carefully by considering incipient criterion, instantaneous velocity, relative exposure degree of bed material on the surface of river bed, as well as, virtual mass force, etc. The formula for critical shear stress of non-cohesive sediment is obtained by rolling model,
as:. The coefficient of relative degree of exposure ζ, and a synthesize influence
coefficient A correlated with flow fluctuation, drag, lift, and submerged gravity and their arm etc. are included.
The coefficient of A is calculated by using related data available in existing research findings. The critical shear stress is not a constant even for uniform sediment and depends on the relative exposure degree of sand. For non-uniform bed material, sediment particle with diameter larger than equilibrium one, may move easily. The situation is on the contrary for the sediment particle with diameter less than the equilibrium one. And the sediment particle with diameter equal to equilibrium one have the same incipient velocity with uniform sediment of equilibrium diameter. The formula is verified with flume data, showing that the calculated results agree well with experiments and may reflect the characteristic of the incipient motion of non-uniform bed material.
出处
《力学学报》
EI
CSCD
北大核心
2003年第3期326-331,共6页
Chinese Journal of Theoretical and Applied Mechanics
基金
国家自然科学基金和水利部联合资助重大项目(59890200)
水利部九五课题资助项目(95-5-4)
兰州铁道学院"青蓝"工程基金资助项目
关键词
泥沙起动
河流动力学
非均匀沙
相对暴露度
水流脉动
临界切应力
non-uniform sediment, incipient velocity, relative degree of exposure, flow fluctuation, additional mass force
