During this study, flow visualization through the use of imaging provided visual data of the events that occurred as the flame oscillated. Imaging was performed in two different ways: 1) the first method was phase-locked imaging to capture a detailed history by simply advancing the phase angle during each image capture, 2) the second method involved high-speed imaging to gather visual image data of a natural or forced oscillating flame. For visualization, two items were considered. The first one was the shape of the flame envelope as it evolved during one oscillation cycle. From the data gathered, it was confirmed that the flame stretched in the vertical direction before quenching in the region near its center. The second consideration was imaging of the oxidizer (air) in the region immediately outside the flame. This was done by imaging the laser light reflected from particles seeded into the flow, which revealed formation of vortical structures in those regions where quenching had occurred. It was noted that quenching took place primarily by the entrainment of fresh non-reacting air into the flame. The quenching process was in turn responsible for the oscillatory behavior.

中文翻译：

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闪烁的甲烷/空气扩散火焰中火焰行为的成像

在这项研究中，通过使用成像的流动可视化提供了火焰振荡时发生的事件的可视化数据。成像以两种不同的方式进行：1) 第一种方法是锁相成像，通过在每次图像捕获期间简单地推进相位角来捕获详细的历史，2) 第二种方法涉及高速成像以收集视觉图像数据自然或强制振荡的火焰。为了可视化，考虑了两个项目。第一个是火焰包络在一个振荡周期中演变的形状。从收集到的数据可以确认，火焰在中心附近区域熄灭前在垂直方向上伸展。第二个考虑是对火焰外区域的氧化剂（空气）进行成像。这是通过对从种子流中的粒子反射的激光进行成像来完成的，这揭示了在发生淬火的那些区域形成了涡流结构。注意到淬火主要是通过将新鲜的非反应空气夹带到火焰中而发生的。淬火过程反过来又是造成振荡行为的原因。