气-液两相弹状流广泛存在于核动力工程中,弹状流中液弹特性对弹状流模型的建立具有重要意义。利用高速摄像系统,对竖直窄矩形通道内弹状流中液弹特性进行可视化研究。研究结果表明,窄矩形通道中稳定液弹可分为3个区域:先导气弹尾流区、主流速度分布恢复区和稳定速度分布区。先导气弹尾流区形成机理为先导气弹尾部液膜壁面射流过程。气弹在液弹中所处区域对其特性影响显著;主流为层流及过渡流态时,尾随气弹特性受先导气弹影响显著。在充分发展湍流工况下,液弹中近壁面处轴向速度趋于稳定所需距离等于最小稳定液弹长度Lmin;Lmin随气弹长度增加而增大,随两相雷诺数增加而减小,其变化范围为9Dh-17Dh。
Gas-liquid slug flow is widely encountered in many practical industrial applications. A de- tailed understanding of the hydrodynamics of the liquid slug has important significance for modeling slug flow. A high speed video camera system is applied to visually study the liquid-slug characteristics of slugflow in a vertical narrow rectangular channel (3.25×40mm^2). It is found that the stable liquid slug in the nar- row rectangular channel consists of three regions: wake region of leading slug, recovering region of the ve- locity profile to main flow, stable main flow region. The wake region of leading slug is resulted from the jet of the wall liquid film in the wake of leading gas slug. The position of trailing gas slug in the liquid slug has significant influence on its characteristics. The leading slug also has enormous effect on the trailing slug in laminar or transition flow. The minimum stable liquid slug length Lmin is referred to the length of axial veloc- ity profile near wall region in the liquid slug approaching to fully developed turbulence region (ReTP〉9000), Lmin increases with increasing slug length and varies inversely with two-phase Reynolds number, and it is in the range of 9-17Dh.