# Experimental Study on Anti-Icing Performance of NS-DBD Plasma Actuator
## 1 Introduction  
Icing can seriously threaten the safety and performance of aircraft [1; 2]. According to statistics from the AOPA Aviation Safety Foundation, in the decade between 1990 and 2000, about 3230 flight accidents occurred because of weather conditions, among which 388 were related to ice accretion, i.e., about 12% of the total [3]. The aerodynamic shape of the aircraft is compromised when microsized, supercooled water droplets impinge and freeze on the wing surface, resulting in an increase in drag and a decrease in lift [4]. Meanwhile, ice formation on the compression inlets of air-breathing engines would cause a reduction of intake air, or even a blockage, which leads to thrust reduction or even causes the aircraft's engine to stall [5]. Therefore, aircraft icing has always been recognized as a significant hazard for modern aircraft. Accumulated ice can be generally classified as one of prime ice, glaze ice, and mixed ice. Rime ice is always formed at lower temperatures (\(-\)40 \({}^{\circ}\)C to \(-\)10 \({}^{\circ}\)C), as relatively small supercooled water droplets freeze almost immediately onto the surface. Glaze ice occurs at relatively higher temperatures(\(-10\)\({}^{\circ}\)C to \(0\)\({}^{\circ}\)C) as relatively larger droplets impact the surface, run back as a thin liquid film, and then freeze; this is considered the most dangerous type of ice. Most mixed ice is formed between \(-20\)\({}^{\circ}\)C and \(-10\)\({}^{\circ}\)C.  
To date, numerous anti-icing and de-icing methods have been proposed to overcome the icing problem, such as electro-impulse de-icing systems, hot air anti-icing systems, electric heating deicing systems, and anti-icing fluid technology [6; 7; 8]. Superhydrophobic surfaces have also been widely studied to prevent the formation of ice [9]. Electro-impulse de-icing systems can create a high amplitude and very short duration of force on the skin. Using this approach, the ice accumulated on the wing would be broken and detach from the target surface [10]. However, acting directly on the skin will affect the service life of the aircraft. Both the hot air and the electric heating deicing systems work through heating the outer surface, causing a reduction in engine propulsion efficiency and huge power consumption [11; 12]. Anti-icing fluid technology would affect the carrying capacity of an aircraft [13]. Thus, it is urgent to find a new approach for ice control [14]. The target anti-/de-icing method is expected to have low energy consumption, low weight, high anti-/de-icing efficiency, and so on. In recent years, extensive research studies have focused on the active flow control performance of the dielectric barrier discharge (DBD) actuator, due to its fairly simple layout, lack of mechanical elements, and relatively low power consumption [15; 16; 17]. Generally, the DBD plasma actuator is composed of two metal electrodes separated by a thin dielectric layer, as shown in Figure 1.  
Two types of plasma actuators were widely investigated. One is driven by high AC (alternating current) sine voltage with a frequency of several kilohertz, called AC-DBD plasma actuator. The other is the NS-DBD plasma actuator, which is ignited by repetitive high voltage pulses with fast rising times (in nanoseconds) [18]. Different from boundary layer acceleration of AC-DBD plasma actuation, the work principle of NS-DBD plasma actuation for flow control is generally considered as ultrafast heating within the discharge volume. A large portion of energy is momentarily deposited into the proximity of the discharge filaments, which is partially converted into the gas heating, resulting in a sudden temperature jump inside the discharge volume [19]. Subsequently, pressure waves are formed with two parts. A straight region at the top of a hemispheric region located at the edge of the exposed electrode was observed, as shown in Figure 2[20; 21]. As revealed by [PERSON] et al. [22], the length of the straight part of pressure waves is well matched with the extended distance of plasma filaments.