Abstract Flow dynamics of two-dimensional liquid sheets discharged into low-speed gaseous crossflow were experimentally investigated. The flow characteristics of liquid sheets were visualized by taking advantage of diffused backlight shadowgraphy and high-speed photography. Three injectors with an equal thickness of 0.35 mm and aspect ratios of 30, 60 and 90 were manufactured and tested at different flow conditions. A full discussion about the flow characteristics of two-dimensional liquid sheets in the presence of transverse airflow is provided. Visualizations revealed that the liquid sheets represented a unique concave-like structure that was named as inflated sheet. This special characteristic was not previously seen on any other circular or non-circular liquid jets and therefore made the flow dynamics of liquid sheets in subsonic crossflow very distinguished. The inflated sheet was found to transform from an enclosed structure into an open structure. The open inflated sheet was disturbed by different breakup mechanisms including sheet rupture, bag breakup, and Rayleigh–Taylor instability. Based on the observed phenomena, the flow was grouped into five regimes including biconvex, enclosed inflated sheet, open inflated sheet, bag breakup/sheet rupture, and multimode breakup. Furthermore, it was found that the droplet region was bifurcated due to the different breakup mechanisms acting simultaneously upon the sheet. Measurements of sheet trajectory were performed and the effects of momentum ratio and Weber number were studied. It was found that Weber number was only effective at low values, while momentum ratio remarkably impacted the trajectory. Graphic abstract

中文翻译：

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发出亚音速气体横流的二维液体片的可视化

摘要 实验研究了排入低速气体错流的二维液片的流动动力学。通过利用漫射背光阴影成像和高速摄影来可视化液体片的流动特性。制造了三个厚度为 0.35 毫米、纵横比为 30、60 和 90 的喷射器，并在不同的流动条件下进行了测试。对存在横向气流时二维液体片的流动特性进行了全面的讨论。可视化显示，液体片代表了一种独特的凹状结构，称为膨胀片。这种特殊的特性以前在任何其他圆形或非圆形液体射流上都没有看到，因此使得亚音速横流中液体片的流动动力学非常独特。发现充气板从封闭结构转变为开放结构。开放的充气床单受到不同破裂机制的干扰，包括床单破裂、袋子破裂和瑞利-泰勒不稳定性。根据观察到的现象，流动分为五种状态，包括双凸面、封闭式充气片、开放式充气片、袋破裂/片破裂和多模破裂。此外，发现液滴区域由于同时作用在片材上的不同破碎机制而分叉。进行了片材轨迹的测量，并研究了动量比和韦伯数的影响。发现韦伯数仅在低值时有效，而动量比显着影响轨迹。图形摘要