A comparative study of alternating current and nanosecond plasma actuators in flow separation control
A comparative study of alternating current and nanosecond plasma actuators in flow separation control
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DOI：
10.1016/j.ijheatmasstransfer.2019.02.030
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发表时间：
2019-06
影响因子：
5.2
通讯作者：
J. Zheng;Y. Cui;B. Khoo
中科院分区：
文献类型：
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作者：
J. Zheng;Y. Cui;B. Khoo
结合数值模拟和实验研究，阐明交流（ac）和纳秒（ns）等离子体激励器之间的流动分离控制机制的差异。重点是可视化详细的流致动过程，并建立流控制权限与不同致动器特性之间的关系。采用时间分辨粒子图像测速（PIV）技术，对低雷诺数（Re）为6.3 × 104的失速NACA 0015翼型的瞬态分离流场进行了测量，并对等离子体激励下的流场进行了响应分析。在Re =（0.063，0.75）× 106时，对低雷诺数和高雷诺数两种情况进行了雷诺平均二维计算，以补充实验。利用精细的Reynolds应力湍流模型，结合表面交流等离子体放电的经验体力模型和ns脉冲放电的复杂自相似公式，我们已经能够数值再现实验观察到的复杂机制，例如不稳定剪切层离散成单个涡，大尺度展向涡的形成，强卷吸效应和流动正则化方法。此外，来自模拟的信息使我们能够进行许多没有实验对应的重要观察。详细的模拟表明，纳秒放电产生的余热与横流的对流使纳秒等离子体激励器在扰动远下游流体方面比其他激励器更灵活，在某些高雷诺数的流动中表现出上级的优越性。在一定的强迫频率范围内，出现了较强的流动共振和频率锁定现象。此外，连续交流等离子体执行器似乎有复杂的控制机制，这取决于流动条件。
A combined numerical and experimental study is performed to elucidate the difference in flow separation control mechanisms between alternating current (ac) and nanosecond (ns) plasma actuators. The focus is on the visualization of detailed flow actuation process and establishment of relationship between flow control authority and characteristics of different actuators. Time-resolved particle image velocimetry (PIV) system is used to capture the transient separated flow over a stalled NACA 0015 airfoil at low Reynolds number (Re) of 6.3 × 104and response of the flow to plasma actuation. Reynolds-averaged two-dimensional computation is performed for both low and high Reynolds number cases atRe= (0.063, 0.75) × 106to complement experiment. Utilizing the elaborate Reynolds stress turbulence model in conjunction with an empirical body force model for surface ac plasma discharge and a sophisticated self-similar formulation for ns pulsed discharge, we have been able to numerically reproduce the experimentally observed intricate mechanisms, e.g. discretization of unstable shear layer into individual vortices, formation of large-scale spanwise vortex, strong entrainment effect of vortices and flow regularization procedure. Moreover, the information from simulation allows us to make a number of important observations which have no experimental counterparts. The detailed simulation shows that the convection of residual heat from ns discharge with cross flow makes ns plasma actuator more flexible in perturbing far downstream fluid in comparison with other actuators, and makes it superior to other devices in some highRenumber flows. Also observed is the occurrence of strong flow resonance and frequency lock-in at a proper range of forcing frequency. In addition, the continuous ac plasma actuator appears to have complex control mechanisms, depending on flow conditions.