The present work experimentally investigates two forcing strategies toward controlling stationary crossflow instability (CFI) induced transition manifesting on a swept wing at subsonic conditions. The effectiveness of upstream flow deformation (UFD) and the base-flow modification strategies, realized through the application of spanwise-modulated and spanwise-uniform dielectric barrier discharge plasma actuation, respectively, is compared experimentally. Specialized, patterned actuators that generate spanwise-modulated plasma jets have been fabricated using a spray-on technique and positioned near the leading edge. An array of discrete roughness elements (DREs) is installed upstream of the plasma forcing to lock the origin and evolution of the critical stationary CFI vortices in the boundary layer. The impact of the phase relation between the spanwise-modulated plasma jets and the incoming CFI vortices is inspected. Infrared thermography is employed to detect and quantify the transition location. A delay in transition is observed with all tested forcing configurations. However, as the incoming CFI vortices are highly amplified due to the application of DREs, the acquired results suggest that with spanwise-modulated forcing the control mechanism responsible for the observed transition delay is not purely UFD; rather the beneficial effects observed leverage on a combination of direct attenuation of the CFI vortices and localized base-flow modification, depending on the aforementioned phase relation. For all forcing strategies and configurations, a simplified drag reduction efficiency estimation is performed using the experimentally measured transition location and the electrical power use of the actuators. A net gain is found for selected configurations.

本工作通过实验研究了两种控制策略，以控制在亚音速条件下在掠过的机翼上出现的平稳横流不稳定性（CFI）诱导的过渡。通过实验比较了分别通过沿展向调制和沿展向均匀的介质阻挡放电等离子体致动实现的上游流动变形（UFD）和基流修正策略的有效性。已经使用喷涂技术制造了产生跨度调制的等离子流的专门的带图案的执行器，并定位在前缘附近。在等离子强制上游安装了一系列离散粗糙度元素（DRE），以锁定边界层中关键的固定CFI涡旋的起源和演变。检查了跨度调制等离子体射流和传入CFI涡旋之间的相位关系的影响。红外热像仪用于检测和量化过渡位置。在所有测试的强制配置中都观察到转换延迟。但是，由于DRE的应用，传入的CFI涡流被高度放大，因此获得的结果表明，采用跨度调制强制时，负责观察到的转换延迟的控制机制并非纯粹是UFD。相反，观察到的有益效果取决于CFI涡旋的直接衰减和局部基流修正的组合，具体取决于上述相位关系。对于所有强制策略和配置，使用实验测量的过渡位置和执行器的电力使用量，可以简化减阻效率。找到选定配置的净收益。