粗糙床面紊动产生机理初探

Study on the Mechanism of Turbulent Production over a Rough Bed

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。结果表明:对于完全粗糙床面,当H/k>1.0时,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/k<1.0,即对于大尺度粗糙,紊动产生的途径有待进一步研究。

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.