Spatial arrangement of vortex-generator-type plasma actuator for separation control of airfoil flow

In this study, large-eddy simulations on separated-airfoil-flows controlled using a vortex-generator-type plasma actuator (VG-PA) have been conducted. The flow conditions, airfoil shape, and the configurations of the VG-PA were set based on a previous experimental study by Jukes et al. [AIAA J. 51, 452 (2013)]. The Reynolds number based on the chord length (c) was set at 95 000 with an angle of attack of 18°. The VG-PA spanwise spacing (λ/c) was varied from 0.05 to 0.4. The results show that the improvement in the aerodynamic performances by the VG-PA control is significantly affected by λ/c. The most effective airfoil flow control was achieved at λ/c=0.1. In the controlled cases, large-scale streamwise flow structures were generated by the interaction of the streamwise vortices produced by the VG-PA. These structures were formed with fine-scale three-dimensional turbulent vortices, resulting in negative Reynolds stress and turbulent reattachment. Furthermore, the streamwise vortex generated by the VG-PA in a boundary layer flow was investigated to better understand the distribution of vortices. The streamwise vortex was distributed from the actuator to a point 0.1c away from the actuator in the induced flow direction. This indicates that the most effective airfoil flow control to improve the aerodynamic performances can be achieved when the streamwise vortex generated by the VG-PA collides with the opposite streamwise vortex.