PARTICLE CHARGING EFFECTS ON PIV MEASUREMENTS OF PLASMA ACTUATORS

Abstract

Plasma actuators gained popularity during the change of the millennium for their ability to induce airflow and reattach stalled flow. Since then, investigations have been conducted to characterize their performance and extend their applications. Plasma actuators can be used to increase lift, decrease drag, and increase the efficiency of wind turbines. Phase locked ensemble averaging particle image velocimetry (PIV) is used to determine the induced velocity field and characterize actuator behavior and performance. However, very few studies account for particle charging from dusty plasma theory. Particle charging theories for high pressure plasmas predict a mostly linear trend between charge and particle size, with smaller particles charging less. In this work, PIV experiments were conducted with monodisperse nanoparticles for sizes ranging between 300 nm and 1250 nm. Results showed that smaller particles follow the flow more closely. PIV uncertainty quantification was performed for ensemble averaging processing. A weighted linear fit was applied to each vector and extrapolated to the 0 nm particle speed, which is taken as the true air speed. Stokes drag force fields were calculated using the known velocity difference, and using a force balance calculation the electrostatic force acting on the particles was calculated. The electrostatic force near the actuator electrode was always acting upstream, implying that particles can attain either negative or positive charge, depending on the phase.