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首页> 外文期刊>International Journal of Heat and Mass Transfer >Perturbation of a laminar boundary layer by a synthetic jet for heat transfer enhancement
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Perturbation of a laminar boundary layer by a synthetic jet for heat transfer enhancement

机译：合成射流对层流边界层的扰动，以增强传热

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An experimental investigation of a cross-flow interaction between a synthetic jet and a flat plate laminar boundary layer is reported. The synthetic jet uses a piezo-actuator for displacing the diaphragm, thus enabling flow control in terms of the excitation amplitude and the modulation frequency. The role of these parameters on heat transfer enhancement from the flat plate is investigated. Measurements are carried out using hotwire anemometry for the flow field while the heat transfer coefficient and jet spreading are imaged respectively by liquid crystal thermography and the laser schlieren technique.rnResults show that the average heat transfer coefficient increases with excitation amplitude and a maximum of 44% enhancement is observed. Amplitude modulation at low frequencies also increases the heat transfer coefficient. Overall, the study indicates the efficacy of a synthetic jet actuator for heat transfer enhancement with excitation amplitude and modulation frequency as control parameters.rnVisualization using liquid crystal thermography shows dual streaks over the flat surface indicating the footprint of vortical structures from the synthetic jet inside the laminar boundary layer. The role played by amplitude modulation in enhancing heat transfer is clearly demonstrated by schlieren visualization and further confirmed by hotwire measurements. The synthetic jet also increases the average turbulence content inside the boundary layer. Power spectra show an overall increase in the amplitude of the low frequency fluctuations arising from synthetic jet actuation. The time-averaged velocity profile behind the synthetic jet shows similarity to the wake profile behind a surface-mounted obstacle. Analogous to physical obstacles such as ribs, these results show that a synthetic jet can also be used as a device for heat transfer enhancement in a boundary layer.
机译：报道了对合成射流和平板层流边界层之间的横流相互作用的实验研究。合成射流使用压电致动器来移动隔膜，从而可以根据激励幅度和调制频率进行流量控制。研究了这些参数对增强平板传热的作用。使用热线风速仪对流场进行测量，同时通过液晶热成像法和激光schlieren技术分别对传热系数和射流扩展进行成像。结果表明，平均传热系数随激发幅度而增加，最大值为44％观察到增强。低频振幅调制也会增加传热系数。总体而言，该研究表明了以激励振幅和调制频率作为控制参数的合成射流致动器在增强传热方面的功效。使用液晶热成像技术进行可视化显示，在平坦表面上存在双重条纹，表明合成射流内部的旋涡结构的足迹层流边界层。 schlieren可视化清楚地证明了幅度调制在增强传热中的作用，并通过热线测量进一步证实了这一点。合成射流还会增加边界层内部的平均湍流含量。功率谱显示出由合成射流致动引起的低频波动幅度的整体增加。合成射流后的时均速度曲线与表面安装障碍物后的尾流曲线相似。类似于肋等物理障碍，这些结果表明，合成射流也可以用作边界层中传热增强的装置。

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