Tailoring the Wall Jet from an Aerodynamic Plasma Actuator through Electrode Modifications

Plasma actuators are potentially very useful in bou ndary layer control on airfoil surfaces. Recent work measuring the forces acting on the plas ma actuator, however, indicates that much of the force produced by the aerodynamic plasma actuator is lost due to shear stress at the surface of the actuator and is not effectively transferred to the air. The effectiveness of the actuator could be increased if the momentum coupling between charged and neutral particles is moved farther from the surface. Three exposed electrode designs were evaluated in this study to demonstrate that momentum could be produced farther from the surface; a standard single plate actuator, a wire and plate ac tuator, and an epoxy-coated actuator. The epoxy coating covered almost the entire exposed ele ctrode and was used to control electron flow. The actuators were each operated at an AC voltage of 15kV and 200Hz in still air. Flow field velocities were measured through a PIV system, taking phase-locked pictures at 12 different times along the operating voltage cycl e to demonstrate the unsteady behavior of the flow. The PIV system captured images at seven different positions along the surface of the actuator, from 2 cm upstream of the exposed ele ctrode to 5 cm downstream, to provide a broad view of the flow behavior. At each data poin t 100 PIV pairs are taken to ensure reasonable average results. The PIV data revealed f low acceleration during the forward stroke of the voltage cycle but almost none during the back stroke. The epoxy-coated actuator moved a much thicker region of air than the standard actuator did. The peak velocity for the jet produced by epoxy-coated actua tor was much less than peak velocity produced the standard of wired actuators. The momentum flux from the epoxy‐coated actuator was the same as the wire actuator but less than the standard actuator.