The phenomenon of foam formation by air entrainment of impinging water jet is reported in this paper. An effort has been made to understand the physics of the phenomenon through visual and photographic observations. The formation of an air sheath and downward motion of the impinging jet are reported. Experimental visualization of the mechanism of air entrainment by foam formation at low jet flowrates of $$8.33 \times 10^{ - 6} - 1.83 \times 10^{ - 6} {\text{m}}^{3} /{\text{s}}$$ for jet lengths of 13, 18, 23 and 25 cm, respectively, was performed with a vertically free-falling jet. Foam formation via air entrainment has been classified into four types: no entrainment, incipient entrainment, intermittent entrainment and continuous entrainment with increases in jet impinging velocity with fixed jet length. Foam formation depends on the impinging jet velocity, nozzle design, impinging jet length and physical property of the jet such as the surface tension which constitutes the major controlling factors for foam formation via air entrainment of impinging jet.

中文翻译：

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垂直自由下落撞击水射流泡沫形成的可视化

本文报道了冲击水射流夹带空气形成泡沫的现象。已经努力通过视觉和摄影观察来了解这种现象的物理学。报告了空气鞘的形成和撞击射流的向下运动。在 $8.33 美元的低射流流速下通过泡沫形成夹带空气机制的实验可视化 \times 10^{ - 6} - 1.83 \times 10^{ - 6} {\text{m}}^{3} /{\ text{s}}$$ 的喷射长度分别为 13、18、23 和 25 厘米，使用垂直自由落体喷射。通过空气夹带形成的泡沫已分为四种类型：无夹带、初期夹带、间歇夹带和在固定射流长度下随着射流撞击速度增加而连续夹带。