The effects of Reynolds number on flow and mixing characteristics of a merged single swinging jet induced by a V-shaped fluidic oscillator were studied experimentally. The jet Reynolds number was varied from 80 to 3000. A high-speed digital camera was used to capture the instantaneous flow evolution processes using the laser light-sheet-assisted flow visualisation method. Long-exposure images together with the binary edge detection technique were used to identify the jet spread width. The velocities, turbulence intensities, as well as turbulence macro time and length scales in the central axis were measured using a one-component hot-wire anemometer. Measurement results using the tracer-gas concentration detection method provided information on the dispersion characteristics of the merged swinging and non-swinging jets. Four characteristic flow modes (non-swinging, subcritical swinging, critical swinging, and supercritical swinging jets) were identified within different ranges of jet Reynolds number. At Reynolds numbers <150 ± 10, no jet swinging happened. At Reynolds numbers between 150 ± 10 and 1200 ± 23, the instantaneous velocities of the merged jet presented periodic oscillations of small amplitudes and was denoted as the subcritical swinging jet. At Reynolds numbers between 1200 ± 23 and 2350 ± 50, the merged jet proceeded irregular swinging motion and was called the critical jet. At Reynolds numbers higher than 2350 ± 50, the time-evolving velocities of the merged jet presented periodic oscillations of large amplitudes imposed by large turbulent fluctuations and was termed the supercritical swinging jet. The measured results of the axial velocities and turbulence intensities in the central axis revealed that in the regime of the supercritical swinging jet, the momentum conversion from the axial to transverse direction was rapidly performed in the near field at the axial distance <2.4 times of the jet exit width due to the induced transverse jet oscillation. The transverse oscillations of the swinging jets induced large turbulence intensities and small turbulence macro time and length scales, and led to large jet mass dispersion. Therefore, the mixing characteristics of the flow was significantly improved due to large jet mass dispersion.

中文翻译：

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雷诺数对自持摆动射流流动和混合特性的影响

实验研究了雷诺数对 V 型流体振荡器诱导的合并单摆动射流的流动和混合特性的影响。射流雷诺数从 80 到 3000 不等。高速数码相机用于使用激光片辅助流动可视化方法捕获瞬时流动演变过程。长时间曝光图像与二进制边缘检测技术一起用于识别射流扩散宽度。使用单分量热线风速计测量中心轴的速度、湍流强度以及湍流宏观时间和长度尺度。使用示踪气体浓度检测方法的测量结果提供了关于合并的摆动和非摆动射流的分散特性的信息。在射流雷诺数的不同范围内确定了四种特征流动模式（非摆动、亚临界摆动、临界摆动和超临界摆动射流）。在雷诺数 <150 ± 10 时，没有发生喷射摆动。在雷诺数介于 150 ± 10 和 1200 ± 23 之间时，合并射流的瞬时速度呈现小幅度的周期性振荡，并表示为亚临界摆动射流。在雷诺数在 1200±23 和 2350±50 之间时，合并的射流进行不规则的摆动运动，称为临界射流。在雷诺数高于 2350±50 时，合并射流的时间演化速度呈现出由大湍流波动施加的大振幅周期性振荡，被称为超临界摆动射流。中心轴轴向速度和湍流强度的测量结果表明，在超临界摆动射流状态下，在近场轴向距离<2.4倍处，从轴向到横向的动量转换迅速。由于引起的横向射流振荡而导致的射流出口宽度。摆动射流的横向振荡引起大的湍流强度和小的湍流宏观时间和长度尺度，并导致大的射流质量弥散。因此，由于大射流质量分散，流动的混合特性得到显着改善。由于诱导的横向射流振荡，在轴向距离<射流出口宽度的2.4倍的近场中，从轴向到横向的动量转换迅速进行。摆动射流的横向振荡引起大的湍流强度和小的湍流宏观时间和长度尺度，并导致大的射流质量弥散。因此，由于大射流质量分散，流动的混合特性得到显着改善。由于诱导的横向射流振荡，在轴向距离<射流出口宽度的2.4倍的近场中，从轴向到横向的动量转换迅速进行。摆动射流的横向振荡引起大的湍流强度和小的湍流宏观时间和长度尺度，并导致大的射流质量弥散。因此，由于大射流质量分散，流动的混合特性得到显着改善。