Time-variant planar laser-induced fluorescence for thickness measurement of wavy liquid films: a calibration-free and threshold-free method

IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL
Yoshiaki Kamada, Zhenying Wang, Chihiro Inoue, Shigeki Senoo
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引用次数: 0

Abstract

The planar laser-induced fluorescence (PLIF) method has been widely applied for measuring the thickness of liquid films. To identify the liquid–gas interface, however, PLIF-based methods require an artificial threshold value of brightness or a calibration curve between the thickness and the brightness, limiting its application in measuring unknown film thickness. To overcome the drawbacks, we propose a new method, time-variant PLIF (T-PLIF), which employs an index of time variance of brightness to detect the interface. We first establish the mathematical principle of T-PLIF, wherein the time variance of a phase-dependent variable becomes the maximum exactly at the time-averaged position of the wavy interface. We then perform experiments for a well-controlled downward annular liquid film flow to test the reliability of T-PLIF. We demonstrate that T-PLIF measures liquid film thickness of \(h > 0.2\,\textrm{mm}\) with the accuracy of \(\varepsilon \le 10\%\) to the theoretical reference and \(h \le 0.2\,\textrm{mm}\) with \(\varepsilon = 20\%\). T-PLIF is able to quantify the film thickness with no need for any pre-/post-calibration or artificial threshold values. We further confirm the applicability of T-PLIF to the wavy film flow sheared by an airflow up to \(30\,\text{m/s}\) by measuring the phase velocity and wavelength, which well matches the theoretical results.

Abstract Image

时变平面激光诱导荧光测量波浪状液体膜厚度:一种无校准和无阈值的方法
平面激光诱导荧光(PLIF)法被广泛应用于液体膜厚度的测量。然而,为了识别液气界面,基于plif的方法需要人为的亮度阈值或厚度与亮度之间的校准曲线,这限制了其在测量未知膜厚度方面的应用。为了克服这些缺点,我们提出了一种新的方法——时变PLIF (T-PLIF),该方法利用亮度的时变指标来检测接口。我们首先建立了T-PLIF的数学原理,其中相位相关变量的时间方差恰好在波状界面的时间平均位置成为最大值。然后,我们进行了控制良好的向下环形液膜流动的实验,以测试T-PLIF的可靠性。我们证明了T-PLIF测量液膜厚度\(h > 0.2\,\textrm{mm}\)的精度为\(\varepsilon \le 10\%\),与理论参考的精度为\(h \le 0.2\,\textrm{mm}\),与\(\varepsilon = 20\%\)的精度为。T-PLIF能够量化薄膜厚度,无需任何前/后校准或人工阈值。通过测量相速度和波长,进一步证实了T-PLIF对高达\(30\,\text{m/s}\)气流剪切的波状膜流的适用性,与理论结果吻合较好。
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来源期刊
Experiments in Fluids
Experiments in Fluids 工程技术-工程:机械
CiteScore
5.10
自引率
12.50%
发文量
157
审稿时长
3.8 months
期刊介绍: Experiments in Fluids examines the advancement, extension, and improvement of new techniques of flow measurement. The journal also publishes contributions that employ existing experimental techniques to gain an understanding of the underlying flow physics in the areas of turbulence, aerodynamics, hydrodynamics, convective heat transfer, combustion, turbomachinery, multi-phase flows, and chemical, biological and geological flows. In addition, readers will find papers that report on investigations combining experimental and analytical/numerical approaches.
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