Vectoring of parallel synthetic jets: a parametric study
Vectoring of parallel synthetic jets: a parametric study
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DOI：
10.1017/jfm.2016.559
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发表时间：
2016-09
影响因子：
3.7
通讯作者：
T. Berk;G. Gomit;B. Ganapathisubramani
中科院分区：
文献类型：
--
作者：
T. Berk;G. Gomit;B. Ganapathisubramani
一对平行合成射流的矢量化可以用五个无量纲参数来描述：狭缝的纵横比，Strouhal数，雷诺数，射流之间的相位差和狭缝之间的间距。在本研究中，后四个对射流的矢量行为的影响进行了实验研究，使用粒子图像测速仪。时间平均速度图被用来给出一个定性的描述矢量的变化，为参数扫描的四个参数独立。观察到一组不同的矢量化行为，其中产生的射流可以合并或分叉，并且可以朝向相位领先的致动器或相位滞后的致动器矢量化。定义了三个性能指标来定量描述矢量化行为：分叉分支之间的夹角，总流量的矢量化角度和流量的归一化动量通量。使用这些指标，斯特劳哈尔数，雷诺数，相位差和间距的变化的影响进行量化。相位锁定的旋涡强度的地图被用来跟踪涡对。涡轨迹被用来定义三个斯特劳哈尔数制度的矢量行为。在第一个政权中，矢量行为是由夹断时间，这是作为斯特劳哈尔数的函数只写占主导地位。在第二个政权，夹断时间是不变的，矢量的行为略有变化与Strouhal数。在第三区域，由形成标准给出，没有合成射流形成。在一个单一的阶段，后不久创建的滞后涡对涡的位置，被用来提出一个矢量机制。这种矢量化机制解释了观察到的所有四个参数的定性和定量变化。
The vectoring of a pair of parallel synthetic jets can be described using five dimensionless parameters: the aspect ratio of the slots, the Strouhal number, the Reynolds number, the phase difference between the jets and the spacing between the slots. In the present study, the influence of the latter four on the vectoring behaviour of the jets is examined experimentally, using particle image velocimetry. Time-averaged velocity maps are used to give a qualitative description of the variations in vectoring for a parametric sweep of each of the four parameters independently. A diverse set of vectoring behaviour is observed in which the resulting jet can be merged or bifurcated and either vectored towards the actuator leading in phase or the actuator lagging in phase. Three performance metrics are defined to give a quantitative description of the vectoring behaviour: the included angle between bifurcated branches, the vectoring angle of the total flow and the normalized momentum flux of the flow. Using these metrics, the influence of changes in the Strouhal number, Reynolds number, phase difference and spacing are quantified. Phase-locked maps of the swirling strength are used to track vortex pairs. Vortex trajectories are used to define three Strouhal number regimes for the vectoring behaviour. In the first regime, vectoring behaviour is dominated by the pinch-off time, which is written as function of Strouhal number only. In the second regime, the pinch-off time is invariant and the vectoring behaviour slightly changes with Strouhal number. In the third regime, given by the formation criterion, no synthetic jet is formed. Vortex positions at a single phase, shortly after creation of the lagging vortex pair, are used to propose a vectoring mechanism. This vectoring mechanism explains the observed qualitative and quantitative variations for all four parameters.