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The forcing behavior of a dielectric barrier discharge (DBD) actuator is investigated experimentally using a time-resolved particle image velocimetry (PIV) system in conjunction with a phase shifting technique. The spatio-temporal evolution of the induced flowfield is accurately captured within one high voltage (HV) cycle allowing the calculation of the instantaneous velocity and acceleration. Additional voltage and current measurements provide the power consumption for each case. Four different applied voltage waveform shapes are independently tested, namely, sine, square, positive sawtooth, and negative sawtooth at fixed applied voltage (10 kVpp) and carrier frequency (625 Hz). The instantaneous flowfields reveal the effect of the plasma forcing during the HV cycle. Sine waveform provides large positive forcing during the forward stroke, with minimal but still positive forcing during the backward stroke. Square waveform provides strong and concentrated positive and negative forcing at the beginning of the forward and backward stroke, respectively. Positive sawtooth provides positive but weak forcing during both strokes while the negative sawtooth case produces observable forcing only during the forward stroke. Results indicate the inherent importance of negative ions on the force production mechanisms of DBD’s. Furthermore, the revealed influence of the waveform shape on the force production can provide guidelines for the design of custom asymmetric waveforms for the improvement of the actuator’s performance., Aerodynamics & Wind Energy, Aerospace Engineering

The forcing behavior of a dielectric barrier discharge (DBD) actuator is investigated experimentally using a time-resolved particle image velocimetry (PIV) system in conjunction with a phase shifting technique. The spatio-temporal evolution of the induced flowfield is accurately captured within one high voltage (HV) cycle allowing the calculation of the instantaneous velocity and acceleration. Additional voltage and current measurements provide the power consumption for each case. Four different applied voltage waveform shapes are independently tested, namely, sine, square, positive sawtooth, and negative sawtooth at fixed applied voltage (10 kVpp) and carrier frequency (625 Hz). The instantaneous flowfields reveal the effect of the plasma forcing during the HV cycle. Sine waveform provides large positive forcing during the forward stroke, with minimal but still positive forcing during the backward stroke. Square waveform provides strong and concentrated positive and negative forcing at the beginning of the forward and backward stroke, respectively. Positive sawtooth provides positive but weak forcing during both strokes while the negative sawtooth case produces observable forcing only during the forward stroke. Results indicate the inherent importance of negative ions on the force production mechanisms of DBD’s. Furthermore, the revealed influence of the waveform shape on the force production can provide guidelines for the design of custom asymmetric waveforms for the improvement of the actuator’s performance., Aerodynamics & Wind Energy, Aerospace Engineering

Microplasmas have a number of potential roles to control propagating electromagnetic waves. This report focuses on novel physics of periodic microplasma assembly for electromagnetic media, which is verified by experimental results and analyzed by numerical methods. Using an assembly composed of microplasmas, novel functions are expected due to its complex dielectric function arising from dielectric and lossy properties. The dielectric property creates photonic band gaps, and the lossy property drastically changes transmittance around the photonic band gaps, leading to an attenuation gap. As a result, a “complex” dispersion relation or a band diagram in the three-dimensional space of real and imaginary wavenumbers and wave frequency will open new possibilities to control electromagnetic waves by complex-variable filters composed of microplasma assemblies.

Microplasmas have a number of potential roles to control propagating electromagnetic waves. This report focuses on novel physics of periodic microplasma assembly for electromagnetic media, which is verified by experimental results and analyzed by numerical methods. Using an assembly composed of microplasmas, novel functions are expected due to its complex dielectric function arising from dielectric and lossy properties. The dielectric property creates photonic band gaps, and the lossy property drastically changes transmittance around the photonic band gaps, leading to an attenuation gap. As a result, a “complex” dispersion relation or a band diagram in the three-dimensional space of real and imaginary wavenumbers and wave frequency will open new possibilities to control electromagnetic waves by complex-variable filters composed of microplasma assemblies.