Abstract This experimental study focuses on the characteristics of air-water two-phase interfacial structure of bubbly-to-slug transition flow. Interfacial parameters including void fraction, interfacial area concentration, and bubble interfacial velocity are measured using four-sensor electrical conductivity probe on a 12.7 mm ID vertical tube. The tube size is approximately equal to the maximum distorted bubble size. Therefore, the bubbly-to-slug transition characteristics can be unique from in other sizes of tubes. Comparing with previous studies, this study provides an experimental database with a wide range of the bubbly-to-slug transition regime, with 4 different superficial liquid velocities (0.3, 0.5, 1.0, and 2.0 m/s) and void fraction ranging from 0.07 to 0.66. Experimental results show that the wall-peak void distribution does not appear in a small diameter tube under the bubbly-to-slug flow transition flow. The distribution is related to both void fraction and the relative bubble size to the tube size. In this sense, a new correlation of distribution parameter in the Drift Flux model is proposed based on the previous studies by Ishii, and Hibiki et al. This experimental study can be a good reference for the model development of flow regime transition and the Interfacial Area Transport Equation.

中文翻译：

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12.7 mm 内径垂直管中气泡到段塞过渡流的两相界面结构

摘要 本实验研究了气泡-段塞过渡流的气-水两相界面结构特征。使用四传感器电导率探头在 12.7 毫米 ID 垂直管上测量界面参数，包括空隙率、界面面积浓度和气泡界面速度。管尺寸大约等于最大变形气泡尺寸。因此，气泡到段塞的过渡特性可以是其他尺寸管中独一无二的。与之前的研究相比，本研究提供了一个实验数据库，其中包含范围广泛的气泡到段塞过渡机制，具有 4 种不同的表面液体速度（0.3、0.5、1.0 和 2.0 m/s）和空隙率范围为 0.07到 0.66。实验结果表明，在气泡到段塞流过渡流下，小直径管中不会出现壁峰空隙分布。该分布与空隙率和相对气泡尺寸与管尺寸有关。从这个意义上说，基于 Ishii 和 Hibiki 等人先前的研究，提出了漂移通量模型中分布参数的新相关性。该实验研究可为流态转变和界面面积输运方程的模型开发提供很好的参考。和响等人。该实验研究可为流态转变和界面面积输运方程的模型开发提供很好的参考。和响等人。该实验研究可为流态转变和界面面积输运方程的模型开发提供很好的参考。