Parametric investigation on the effects of plasma streamwise vortex generators on the flow around a bluff body

Abstract

A parameteric study on an array of the plasma streamwise vortex generator (VG) is performed using the semi-empirical thrust model, developed for the dielectric barrier discharge plasma actuators. The counter-rotating-type VG driven by a plasma actuator is attached to the bluff body that has a flat surface and rounded ends to reduce trailing turbulence which contributes a significant portion of the drag. The effects of various parameters, including the length of the VG, force amplitude of the actuator, inter-electrode spacing, position and distance between the VG pairs, are investigated in various freestream conditions from 10 to 50 m/s, which corresponds to Reynolds number range from 140,000 to 700,000. The changes in these parameters significantly affect the performance of the VG; the drag coefficient of the bluff body varies about +10 to -10%. When the drag is reduced, the analysis results show that the trailing vortex, represented in terms of the turbulent kinetic energy term, is also decreased. Longer, densly placed electrodes, and stronger force amplitude are preferred in drag reduction, and nearer positioned VG has a greater influence on the drag. A dimensionless number considering the design parameters and freestream condition is proposed to better describe the behavior of the VG; the drag reduction performance is approximately proportional to the proposed dimensionless number.