# Experimental Study on Anti-Icing Performance of NS-DBD Plasma Actuator
## 2 Experimental Setup  
The experiments were performed in the Icing Research Tunnel available at Nanjing University of Aeronautics and Astronautics. The test section is 350 mm in width \(\times\)400 mm in height. Up to 120 m/s velocity airflow can be generated, and the static temperature can be adjusted, ranging from \(-\)30 \({}^{\circ}\)C to room temperature. Arrays of pneumatic spray nozzles are used to spray micro-sized, supercooled water droplets (ranging from 10-50 \(\upmu\)m in size) into the airflow. Calibration was performed using a laser particle analyzer. The liquid water content (LWC) in the icing wind tunnel is controlled by the number of opened nozzles, which can be adjusted to yield a mist ranging from 0.1 to 3 g/m\({}^{3}\). After calibration and measurement, the wind tunnel maintains good characteristics of airflow field and water droplet field.  
A NACA 0012 airfoil model made of aluminum was used, as shown in Figure 3. The airfoil model has a chord length of 280 mm and spanwise length of 145 mm. The whole surface was covered with 2.5 mm thick PTFE film to prevent heat transfer between the plasma actuator and the airfoil model. The airfoil/wing model was fixed by a stainless-steel rod, oriented horizontally across the middle of the test section. The angle of attack (\(\alpha\)) of the airfoil/wing model was set as \(\alpha=-4.0\) degrees during the anti-icing experiments.  
The NS-DBD plasma actuator was mounted on the front part of the airfoil model, which was applied with plasma actuation. It comprises several 0.027 mm thick copper electrodes (exposed electrodes and buried electrodes) separated by 3 layers of Kapton tape as a dielectric barrier (0.24 mm). Copper electrodes are arranged along the chordwise direction. Along the span direction, there is zero overlap between the exposed and buried electrodes, the spanwise width of which are 2 mm and 10 mm respectively. From the side view of the airfoil model, the buried electrodes were distributed ranging from the airfoil leading edge to around 40 mm from the airfoil chord (at upper surface), and 20 mm from the airfoil chord (at lower surface).  
The exposed electrodes of the plasma actuator were connected to a high-voltage nanosecond pulse power supply, while buried electrodes were grounded (as Figure 4 shows). The power supply used in this experiment can provide a peak-to-peak amplitude of \(V_{P\text{-}p}\) = 0-20 kV, and pulse frequency of \(f_{p}\) = 1-20 kHz. The voltage rise time \(\tau_{r}\), plateau time \(\tau_{p}\) and decaying time \(\tau_{d}\) are all adjustable, as Figure 5 shows. The voltage and current applied to the actuator are measured by a high-voltage probe (Tektronix P6015A, Tektronix, Beaverton, OR, USA) and a current probe (Tektronix P6021, Tektronix, Beaverton, OR, USA) respectively, the results of which were displayed and processed with a Tektronix DPO3054 oscilloscope.  
Surface temperature is measured using a FLIR infrared (IR) imager (SC7300M, FLIR Systems, Wilsonville, OR, USA). The measurement range of the IR camera is \(-20\)\({}^{\circ}\)C to 2000 \({}^{\circ}\)C. The surface emissivity of the Kapton is set as 0.83 [31]. The surface temperature of the exposed copper electrode was not analyzed due to its relatively lower surface emissivity. A CCD camera (Nikon D7000, Nikon Corporation, Tokyo, Japan) positioned on the side of the observation windows was used to record the dynamic ice accretion process at the front part of the airfoil model.  
Figure 3: A NACA 0012 airfoil model.