# Experimental Study on Anti-Icing Performance of NS-DBD Plasma Actuator
## 3 Experimental Results  
### Electrical Diagnostics  
Experiments were conducted on the anti-icing performance of NS-DBD plasma actuator with two different discharge conditions under the same icing condition of airflow speed U = 65 m/s, ambient temperature T = \(-\)10 \({}^{\circ}\)C, liquid water content LWC = 0.5 g/m\({}^{3}\), mean-volume diameter MVD = 25 \(\upmu\)m. In this section, the effect of supercooled water droplets on the discharge morphology is illustrated and discussed.  
As shown in Figure 6a, with no impingement of supercooled water droplets (U = 65 m/s, T = \(-\)10 \({}^{\circ}\)C, LWC = 0 g/m\({}^{3}\)), the discharge filaments are distributed homogeneously, with short plasma lengths along the edge of exposed electrodes when applied with LV-HF discharge (\(V_{p,p}\) = 8.6 kV, \(f_{p}\) = 6 kHz, \(\tau_{t}\) = 200 ns, \(\tau_{p}\) = 300 ns, \(\tau_{d}\) = 200 ns), which causes a distinct dim area between the two adjacent exposed electrodes. In the case of HV-LF discharge (\(V_{p,p}\) = 13.6 kV, \(f_{p}\) = 2 kHz, \(\tau_{t}\) = 200 ns, \(\tau_{p}\) = 300 ns, \(\tau_{d}\) = 200 ns), as Figure 6b shows, the discharge filament further extends towards the middle of exposed electrodes, but the dim areas still exist.  
Figure 7 shows the measured voltage and current waveforms of the NS-DBD plasma actuator from two different discharge conditions. Current pulses are observed in both the rise and decay phases of the applied voltage. As the applied voltage rises, the exposed electrode acts as an anode and a positive ion sheath spread along the dielectric surface, positively charging the dielectric layer surface. In the decay process of applied voltage, the breakdown between the top electrode and the dielectric surface, which has been positively charged by the first pulse, causes the second negative current pulse [23]. The dim area here may be attributed to the effect of surface potential for two adjacent opposite discharges which contain the propagation of discharge filaments when applied with HV-LP discharge. The total power consumption of NS-DBD was computed by the temporal integration of the instantaneous power in one second:  
\[P=\int_{0}^{1}v(t)\cdot i(t)\cdot dt \tag{1}\]  
Figure 4: Schematic illustration of NS-DBD plasma actuator.  
Figure 5: Sketch of a positive nanosecond voltage pulse with rise time \(\tau_{t}\), plateau time \(\tau_{p}\) and decay time \(\tau_{d}\).  
The power consumption of both two discharge conditions is equal to 83 W.  
Figure 6c,d show the effect of supercooled water droplets on the morphology of the two discharge conditions. It can be observed that the plasma discharge is turned to focus on several discharge channels along the electrode edge, and is relatively inhomogeneous. This phenomenon resembles the influence of ambient humidity on AC-DBD in reference [32]. Moreover, under the influence of aerodynamic force, part of the discharge channels was blocked by an unevenly distributed backward flowing water film, resulting in the experimental phenomena that discrete discharge filaments seem to slide backward with the melted backward water film.