基于漂移流模型的矩形通道内泡状流-弹状流转变准则

以空气和水为工质，对竖直向上矩形通道(40 mm×1.41 mm，40 mm×10 mm)两相流流型特性进行了可视化研究。气液相表观速度分别为0.01~0.59 m/s和0.02~3.72 m/s。基于3个经典的泡状流向弹状流转变准则，考虑矩形通道的尺寸效应，导出了泡状流向弹状流转变时的临界空泡份额为0.23。以窄边宽度2.5 mm为界，将矩形通道分为小通道和常规通道两类，对泡状流向弹状流转变准则进行修正，修正准则能很好地预测实验值。为进一步验证修正准则的准确性和适用性，将修正准则与Mishima、Wilmarth和Sadatomi等的实验数据进行了对比，结果显示修正准则同样具有较好的预测效果。

Transitional Criterion From Bubbly Flow to Slug Flow in Vertical Rectangular Channels Based on Drift-flux Model

A visualized study of flow patterns was carried out for air-water two-phase flow in two narrow rectangular ducts (40 mm×1.41 mm, 40 mm×10 mm) respectively. The superficial velocity ranges of air and water were 0.01-0.59 m/s and 0.02-3.72 m/s. Based on three classical criteria on transition from bubbly flow to slug flow, critical transition void fraction 0.23 was deduced by introducing the effect of channel size. The rectangular ducts were classified as small channel (s≤2.5 mm) and conventional channel (s>2.5 mm), based on which a modified transition criterion for bubbly flow to slug flow was proposed. The modified criterion shows a good agreement with the experimental data from this study. Experimental data from Mishima, Wilmarth and Sadatomi etc. were also collected to further evaluate the accuracy and applicability of the modified criterion, showing a good prediction to these experimental data as well.