Abstract A novel moving frame-of-reference brightness-based laser-induced fluorescence (MFoR-BBLIF) method was developed and demonstrated in downwards co-current air–water annular flows. The method was applied to study the downstream development of individual disturbance waves in flows over a range of conditions (Re L = 276–1321, Re G = 39,500–79,000). In this method, the optical measurement system, and hence, the region of interrogation (ROI) was translated physically along the length of the test-section with a velocity close to that of individual disturbance waves to obtain the velocities of individual disturbance-waves as a function of downstream distance from the inlet. It was found that the velocities of individual disturbance waves increase with both downstream distance and gas–liquid flow conditions. In addition, the variation in the wave velocities was more significant at higher gas and liquid Reynolds numbers. The approach can be integrated with many other contactless measurement methods, and can also be used over a range of translation speeds (not necessarily in a “Lagrangian” manner) to study the evolution of important advecting flow phenomena. Graphic abstract

中文翻译：

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用基于移动参考系亮度的激光诱导荧光方法研究向下环状流中扰动波的发展

摘要 开发了一种新的基于移动参考系亮度的激光诱导荧光 (MFoR-BBLIF) 方法，并在向下并流的空气 - 水环流中进行了演示。该方法用于研究在一系列条件下（Re L = 276–1321，Re G = 39,500–79,000）流中单个扰动波的下游发展。在这种方法中，光学测量系统，因此，询问区域 (ROI) 沿着测试段的长度物理平移，其速度接近单个扰动波的速度，以获得单个扰动波的速度为下游距离入口的函数。发现单个扰动波的速度随着下游距离和气液流动条件的增加而增加。此外，在较高的气体和液体雷诺数下，波速的变化更为显着。该方法可以与许多其他非接触式测量方法相结合，也可以在一定的平移速度范围内使用（不一定以“拉格朗日”方式）来研究重要的平流现象的演变。图形摘要