Surface potential and electric field measurements in plasma actuators at low pressure

Aplasma actuator was operated at pressures from 760 to 88 torr to determine the mechanisms leading to decreased force production at low pressures. The actuator was driven with a 5 kHz sine wave and a peak to peak voltage of 13.4 kV. A passive measurement technique called the capacitive V-dot probe was adapted to the actuator to resolve the spatiotemporal evolution of the surface potential and electric field on the dielectric surface. At low pressures up to 20 times more plasma by visual inspection is present than at atmospheric conditions. Average force production is calculated and shown to decrease at lower pressures due to the fact that up to 88% of the plasma is created in regions where the electric field is relatively weak. The calculated average body force shows a slight increase up to a pressure of 429 torr before trending to 0 at lower pressures in good qualitative agreement with experimental force measurements. Performing a power analysis shows that as pressure is decreased more power is used creating plasma rather than accelerating it, leading to a decrease in efficiency.