Abstract The wave characteristics of the turbulent falling liquid film in the development region along the vertical Perspex plate were studied by using an Ultrasonic Doppler Velocimetry (a non-intrusive technique). The instantaneous thickness of the falling film at the center of the plate with axial distance ranges from 50 mm to 1300 mm was measured and the Rel (the liquid film Reynolds number) ranges from 2.28 × 103 to 1.43 × 104. The results show that the mean thickness, wave frequency and amplitude increase while the growth rate decreases with the increase of Rel. The Probability Density Function of the liquid film instantaneous thickness tends to an approximately normal distribution with increasing Rel. Furthermore, the Plateau-Rayleigh instability can cause the breakup of the liquid film surface and resist the increase of the liquid film thickness, which results in the fluctuation range of the liquid film approximate to a fixed value when the Rel > 1.20 × 104.

中文翻译：

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高雷诺数下发育区下降液膜的波动特性

摘要 利用超声波多普勒测速仪（一种非侵入式技术）研究了沿垂直有机玻璃板发展区湍流下落液膜的波动特性。测量轴向距离范围为 50 mm 至 1300 mm 的板中心处降膜的瞬时厚度，Rel（液膜雷诺数）范围为 2.28 × 103 至 1.43 × 104。结果表明随着Rel的增加，平均厚度、波频和波幅增加，而增长率降低。液膜瞬时厚度的概率密度函数随着Rel的增加趋于近似正态分布。此外，