On the formation of streamwise vortices by plasma vortex generators
On the formation of streamwise vortices by plasma vortex generators
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DOI：
10.1017/jfm.2013.418
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发表时间：
2013-10-01
影响因子：
3.7
通讯作者：
Choi, Kwing-So
中科院分区：
文献类型：
--
作者：
Jukes, Timothy N.;Choi, Kwing-So
利用粒子图像测速技术对介质阻挡放电等离子体激励器在层流边界层中产生的流向涡进行了研究，以了解涡的形成机理。等离子体涡流发生器沿着主流动方向定向，以在展向方向上产生体积力。这就产生了一个展向定向的壁面射流，它与迎面而来的附面层相互作用，形成了一个连贯的流向涡。结果表明，来流边界层中的展向涡量向展向壁面射流的外剪切层中发生扭曲和折叠，从而形成流向涡，而展向壁面射流的外剪切层又增加了自身的涡量，从而增大了沿着作动器长度方向的环量。这类似于三角形的叶片型涡流发生器，除了通过在等离子体射流中增加涡流来增强环流。还观察到，等离子体涡形成靠近壁与增强的向壁卷吸，这在致动器上方产生强烈的下洗。
The streamwise vortices generated by dielectric-barrier-discharge plasma actuators in the laminar boundary layer were investigated using particle image velocimetry to understand the vortex-formation mechanisms. The plasma vortex generator was oriented along the primary flow direction to produce a body force in the spanwise direction. This created a spanwise-directed wall jet which interacted with the oncoming boundary layer to form a coherent streamwise vortex. It was found that the streamwise vortices were formed by the twisting and folding of the spanwise vorticity in the oncoming boundary layer into the outer shear layer of the spanwise wall jet, which added its own vorticity to increase the circulation along the actuator length. This is similar to the delta-shaped, vane-type vortex generator, except that the circulation was enhanced by the addition of the vorticity in the plasma jet. It was also observed that the plasma vortex was formed close to the wall with an enhanced wall-ward entrainment, which created strong downwash above the actuator.