Abstract The effect of surface hydrophobicity on the air-water two-phase flow pattern transition was experimentally investigated. Experiments and the two-phase flow visualization were carried out in a hydrophobic polymer tube (4.76 mm ID). The tube material is fluorinated ethylene propylene (FEP) with a hydrophobic surface, and the static contact angle of a water droplet on a smooth surface is 97.28°. The channel surface was roughened to increase the hydrophobicity. The increased surface roughness results in a microstructured surface texture that forms a fine air trapped layer below the liquid droplet on the polymer surface. The channel surface was rotary ground by sandpaper number grit 400, 320, 100, and 80 to develop microstructure textured surface. The measured static contact angle of the roughened surface was 110.7°, 113.26°, 121.03°, and, 126.28° in order of increasing surface roughness. The two-phase flow of the channels with different contact angles was visualized by a high-speed camera and the flow pattern maps were constructed. Even under the same phase superficial velocity conditions, differences in the degree of hydrophobicity lead to transitions to entirely different patterns. The two-phase flow pattern map with the change in hydrophobicity is partitioned by the change in the modified Weber number as a factor indicative of the degree of surface hydrophobicity. The modified Weber number is defined as the ratio of flow inertia to adhesion force, and the new pattern map of the two-phase flow is redefined to take into account the wall hydrophobicity change.

中文翻译：

---

水平管中绝热两相流型转变的表面疏水性变化

摘要 通过实验研究了表面疏水性对气水两相流型转变的影响。实验和两相流可视化在疏水聚合物管 (4.76 mm ID) 中进行。管材为具有疏水表面的氟化乙丙烯（FEP），水滴在光滑表面上的静态接触角为97.28°。通道表面被粗糙化以增加疏水性。增加的表面粗糙度导致微结构表面纹理，在聚合物表面上的液滴下方形成精细的空气捕获层。通道表面用400、320、100和80号砂纸旋转研磨以形成微结构纹理表面。测得的粗糙表面的静态接触角为 110.7°、113.26°、121.03° 和 126。28° 按增加表面粗糙度的顺序。具有不同接触角的通道的两相流通过高速相机进行可视化并构建流型图。即使在相同的相表面速度条件下，疏水性程度的差异也会导致转变为完全不同的模式。具有疏水性变化的两相流型图由作为指示表面疏水性程度的因素的修正韦伯数的变化划分。修改后的韦伯数定义为流动惯性与粘附力的比值，重新定义两相流的新模式图以考虑壁面疏水性变化。具有不同接触角的通道的两相流通过高速相机进行可视化并构建流型图。即使在相同的相表面速度条件下，疏水性程度的差异也会导致转变为完全不同的模式。具有疏水性变化的两相流型图由作为指示表面疏水性程度的因素的修正韦伯数的变化划分。修改后的韦伯数定义为流动惯性与粘附力的比值，重新定义两相流的新模式图以考虑壁面疏水性变化。具有不同接触角的通道的两相流通过高速相机进行可视化并构建流型图。即使在相同的相表面速度条件下，疏水性程度的差异也会导致转变为完全不同的模式。具有疏水性变化的两相流型图由作为指示表面疏水性程度的因素的修正韦伯数的变化划分。修改后的韦伯数定义为流动惯性与粘附力的比值，重新定义两相流的新模式图以考虑壁面疏水性变化。疏水性程度的差异导致转变为完全不同的模式。具有疏水性变化的两相流型图由作为指示表面疏水性程度的因素的修正韦伯数的变化划分。修改后的韦伯数定义为流动惯性与粘附力的比值，重新定义两相流的新模式图以考虑壁面疏水性变化。疏水性程度的差异导致转变为完全不同的模式。具有疏水性变化的两相流型图由作为指示表面疏水性程度的因素的修正韦伯数的变化划分。修改后的韦伯数定义为流动惯性与粘附力的比值，重新定义两相流的新模式图以考虑壁面疏水性变化。