The time-resolved natural flow field of a fluidic oscillator
The time-resolved natural flow field of a fluidic oscillator
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DOI：
10.1007/s00348-015-1993-8
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发表时间：
2015-06
影响因子：
2.4
通讯作者：
R. Woszidlo;Florian Ostermann;C. Nayeri;C. Paschereit
中科院分区：
文献类型：
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作者：
R. Woszidlo;Florian Ostermann;C. Nayeri;C. Paschereit
在不可压缩流态下对具有两个反馈通道的射流振荡器的内部和外部流场进行了实验检查。具有方形出口喷嘴的放大装置提供压缩空气，并向静止环境中发射空间振荡射流。时间分辨信息是通过基于内部参考信号的相位平均压力和 PIV 数据获得的。时间分辨率优于 3° 相位角。对内部动力学的详细分析表明，振荡机制是基于流体流入射流和混合室壁之间的分离气泡，将射流推向另一侧。在一个振荡周期期间通过一个反馈通道输送的流体的总体积与分离气泡从其初始尺寸到其最大程度的总增长相匹配。尽管振荡频率随供电速率线性增加，但仍观察到内部动态的突然变化。这些变化是由反馈通道的逆流增加引起的。发现所发射射流的时间分辨特性，例如瞬时射流宽度和出口速度，在一个振荡周期期间显着振荡。此外，结果表明射流的振荡模式近似为正弦曲线，并且停留时间和切换时间相当。
The internal and external flow field of a fluidic oscillator with two feedback channels are examined experimentally within the incompressible flow regime. A scaled-up device with a square outlet nozzle is supplied with pressurized air and emits a spatially oscillating jet into quiescent environment. Time-resolved information are obtained by phase-averaging pressure and PIV data based on an internal reference signal. The temporal resolution is better than a phase angle of 3°. A detailed analysis of the internal dynamics reveals that the oscillation mechanism is based on fluid feeding into a separation bubble between the jet and mixing chamber wall which pushes the jet to the opposite side. The total volume of fluid transported through one feedback channel during one oscillation cycle matches the total growth of the separation bubble from its initial size to its maximum extent. Although the oscillation frequency increases linearly with supply rate, sudden changes in the internal dynamics are observed. These changes are caused by a growth in reversed flow through the feedback channels. The time-resolved properties of the emitted jet such as instantaneous jet width and exit velocity are found to oscillate substantially during one oscillation cycle. Furthermore, the results infer that the jet’s oscillation pattern is approximately sinusoidal with comparable residence and switching times.