Subsonic flows of different gases in the near field of inert and reacting jets is experimentally investigated. The jets flowed out of long tubes, 2 to 8 mm in diameter, into an air medium at low Reynolds numbers from 400 to 5000. The working fluids were air, carbon dioxide, propane, and Freon-22 for inert isothermal jets and propane mixed with an inert dilution (СО2) for reacting jets. The tools included Hilbert visualization, PIV, thot-wire anemometry, and probe thermometry. A scenario of transition to turbulence through the intermittence mechanism in inert and reacting jets is revealed for the first time. It is realized in the Reynolds number range from 1900 to 3500, when laminar-turbulent transition occurs within the jet source, that is, the tube, in the absence of artificial disturbances. Turbulent spots generated in the tube in the transitional regime are statistical in nature and fairly stable in the jet near-field. Propagating downstream they can have a considerable effect on the dynamics of free jets and diffusion plumes.

中文翻译：

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通过惰性和反应射流的间歇性过渡到湍流

实验研究了惰性和反应射流近场中不同气体的亚音速流动。射流从直径为 2 至 8 毫米的长管中流出，进入雷诺数为 400 到 5000 的低雷诺数的空气介质中。工作流体为空气、二氧化碳、丙烷和氟利昂 22，用于惰性等温射流和丙烷混合用惰性稀释液 (СО2) 用于反应射流。这些工具包括 Hilbert 可视化、PIV、热线风速测量和探针温度测量。首次揭示了通过惰性和反应射流中的间歇机制过渡到湍流的情景。它是在雷诺数范围从 1900 到 3500 中实现的，此时在没有人为干扰的情况下，射流源即管内发生层流-湍流转变。在过渡状态管中产生的湍流点在性质上是统计性的并且在射流近场中相当稳定。向下游传播它们会对自由射流和扩散羽流的动力学产生相当大的影响。