Dielectric Barrier Discharge Plasma Actuator Thrust Measurement Methodology Incorporating Antithrust Hypothesis

The thrust of the dielectric barrier discharge plasma actuator is the plasma body force minus the wall shear force,and it equals the net induced momentum. Thrust measurement simplicity makes it a good metric of the aerodynamicperformance for active flow control applications. Uncertainty and non-repeatability issues with conventional testsetups motivated development of a novel suspended actuator test setup and a measurement methodology consisting ofa burn-in procedure followed by frequency scans at constant voltages. This approach led to observation of negativevalues of thrust, or "antithrust," at low frequencies between 4 Hz and up to 64 Hz. The antithrust is proportional to themean-squared voltage and is frequency independent. Departures from the parabolic antithrust curve are correlatedwith appearance of visible plasma discharges. The antithrust hypothesis is proposed. It states that the measured thrustis the sum of plasma thrust and antithrust. The magnitude of the antithrust depends on the actuator geometry, thematerials, and the test installation. The dependence on test installation was validated by surrounding the actuatorwith a grounded large-diameter metal sleeve.Athrust data correction for antithrust enables meaningful comparisonsbetween actuators at different installations. A strong dependence on humidity is also shown. The thrust significantlydecreases with increasing humidity