Large-eddy simulation of the effect of distributed plasma forcing on the wake of a circular cylinder

Abstract

We conducted large-eddy simulation (LES) to investigate the effect of segmented plasma forcing on the wake of a circular cylinder, at a subcritical Reynolds number of 4700. The action of the plasma actuators was simulated by a body-force model developed by Shyy et al. [1]. The main objective of this study was to investigate the changes in the three-dimensionality of the wake, and the nature of separation on the cylinder surface, with the increasing power of segmented forcing. By observing the three-dimensional (3D) structures, and the separating streamlines close to the cylinder surface, we aim to provide more insight on the experimental findings of Bhattacharya and Gregory [2], which contained only two-dimensional (2D) velocity field data. To that end, we used segmented actuators with a spatial wavelength of 5d (d= cylinder diameter), and two separate blowing ratios of 0.2 and 0.7. At the lower blowing ratio (BR=0.2), spanwise vortex shedding was not canceled, although waviness developed in the spanwise vortices. However, there was no considerable difference in the separation angles between two adjacent spanwise locations. Forcing with higher blowing ratio (BR=0.7) completely disrupted the vortex shedding infront of the plasma region. The separation line on the surface of the cylinder developed significant periodicity leading to a spanwise variation of formation length. We show that such spanwise variation created spatially locked streamwise vortices which disrupted regular vortex shedding.