粗糙床面紊动产生机理初探

在分析已有近壁区光滑床面定性观察和定量测量结果的基础上，对完全粗糙床面明槽湍流偏斜系数Ｓ沿垂线的分布进行了讨论。结构表明：对于完全粗糙床面，当Ｈ／ｋｓ＞１．０，在ｙ／Ｈ＜０．２的范围内有Ｓ＞０，这意味着可能也存在低速条带，即流体紊动亦是由猝发所致；而对于Ｈ／ｋｓ＜１．０，即对于大尺度粗糙，紊动产生的途径有待进一步研究。

Study on the Mechanism of Turbulent Production over a Rough Bed

Based on the analysis of the known quantitative observations and qualitative measurements in the near wall region of the flow over a smooth bed, the distribution of the skewness fastor in the vertical direction has been discussed for the open-channel flow over a fully roughened bed. It is found that when H/k>1.0, S>0 is obtained in the range of y/H< 0.2, which means that there exist the low speed streaks, i. e. the turbulence of the flow is produced by the phenomenon called 'burst'. For H/k, <1. 0, which belongs to the large-scale roughness case, the turbulence will be produced in another way.