明渠水流速度对自掺气发展影响的试验研究

Experimental study on effect of velocity on self-aeration diffusion in open channel flows

采用针式掺气浓度仪对有压出口后明渠水流表面自掺气的发展过程进行了详细测量,研究了不同出口流速条件下掺气发展区的掺气浓度分布及其沿程发展变化情况,分析了流速对自掺气发展的影响。试验结果表明:随着出口流速的增大,相同断面处水流平均掺气浓度不断增加,掺气区向渠道底板扩展更加充分;在断面平均掺气浓度相同的条件下,水流速度越大,水体紊动程度越高,气泡向渠道底板方向扩散越明显。结合紊动扩散理论分析,认为流速对明渠自掺气扩散的影响包括提高水流掺气浓度和增大水体紊动扩散系数两个方面。

This paper presents an experimental study of effect of velocity on self-aeration diffusion in open channel flows.In self-aerated developing region of open channel flow,air concentrations were firstly recorded by a double-tip conductivity probe for dif-ferent initial velocities,and then the effect of velocity on self-aeration development could be investigated.The results show that with the increase of initial velocity of open channel flow,air entrainment increases and mean cross-section air concentration be-comes larger in the water flow.For the same cross-section air concentration condition,the greater the initial velocity,the deeper the self-aeration area developing into the water flow.Based on the turbulent diffusion theory,high velocity can increases the en-trained air content and turbulence intensity coefficient of water flow which improves the self-aeration diffusion in open channel flows.