Crossflow transition control by upstream flow deformation using plasma actuators
Crossflow transition control by upstream flow deformation using plasma actuators
复制标题
DOI：
10.1063/1.4975791
复制
发表时间：
2017-02-14
影响因子：
3.2
通讯作者：
Kloker, Markus J.
中科院分区：
文献类型：
--
作者：
Doerr, Philipp C.;Kloker, Markus J.
采用直接数值模拟的方法，研究了后掠翼型边界层中层流-湍流过渡的控制问题。在我们之前的工作中，我们探索了一种直接基流稳定方法，旨在通过等离子体致动器进行横向均匀流动操纵或直接横流-涡操纵。本文采用了上游流动变形（UFD）技术，该技术的能量输入最小。采用局部体积力建模的致动器被设置为激发比大多数放大模式具有更高的展向波数的放大稳态横流涡（CFV）控制模式。由此产生的非线性控制cfv的间距比自然发生的涡更窄，并且相对于二次不稳定性而言更不稳定。它们产生了有益的平均流畸变，衰减了初级横流的不稳定性，从而延迟了向湍流的过渡。与UFD的粗糙度元件不同，所采用的介质阻挡放电等离子体致动器允许设置力的方向：由于平均横流的减少，对横流施加的力具有直接的、基本的稳定效果，而在横流方向施加的力由于局部平均横流的增加而引起相反的效果。详细讨论了这些设置之间的差异，以及在流向方向上的强迫，并且表明两者确实可以实现显着的过渡延迟，但是具有不同的效率和鲁棒性。此外，还与综合吹吸控制模式的激励设置进行了比较，以阐明直接影响对基流的作用。AIP出版社出版。
Control of laminar-turbulent transition in a swept-wing-type boundary-layer flow, subject to primary crossflow instability, is investigated using direct numerical simulations. In our previous works, we explored a direct base-flow stabilization aimed at a spanwise homogenous flow manipulation or a direct crossflow-vortex manipulation by plasma actuators. In this paper, the technique of upstream flow deformation (UFD) is applied, needing by far the least energy input. The actuators, modeled by local volume forcing, are set to excite amplified steady crossflow vortex (CFV) control modes with a higher spanwise wavenumber than the most amplified modes. The resulting nonlinear control CFVs are spaced narrower than the naturally occurring vortices and are less unstable with respect to secondary instability. They generate a beneficial mean-flow distortion attenuating the primary crossflow instability, and thus a delay of the transition to turbulence. Unlike roughness elements for UFD, the employed dielectric barrier discharge plasma actuators allow to set the force direction: Forcing against the crossflow has a direct, fundamental stabilizing effect due to a reduction of the mean crossflow, whereas forcing in the crossflow direction locally invokes the opposite due to a local increase of the mean crossflow. The differences between these settings, also with respect to forcing in streamwise direction, are discussed in detail, and it is shown that a significant transition delay can be achieved indeed with both, however with a differing efficiency and robustness. Additionally, a comparison to a set-up with an excitation of the control modes by synthetic blowing and suction is performed to clarify the role of the direct effect on the base flow. Published by AIP Publishing.