Aerodynamic noise control by atmospheric pressure glow discharge plasma

Abstract

Summary form only given. Aerodynamic noise control using electrohydrodynamic (EHD) flow induced by atmospheric pressure barrier discharge plasma was demonstrated. EHD flow induced by plasma is caused by the collisions between gas molecules and charged particles accelerated in an electric field. Plasma actuators inducing EHD flow have been developed to control flow on an airfoil or a turbine blade. As aerodynamic noise control using plasma, jet noise reduction by shock wave from arc filament plasma was proposed in the past. Because aerodynamic noise is mainly generated by flow instabilities, a plasma actuator has a potential to control the noise by changing the aerodynamic structure. In this study, an atmospheric pressure glow discharge was used as a plasma actuator using multiple pairs of line electrodes which were placed parallel with an offset on each side of a 1 mm thick glass plate. One side of the electrodes was covered with another glass plate to suppress the surface discharge. The applied voltage of 5 kV peak and 12 kHz sinusoidal wave produced around 0.8 m/sec gas flow near the surface of the electrodes which were not covered. The acoustic noise was measured by a capacitor microphone and flow pattern was observed using a smoke visualization technique. Air jet flow from a small rectangular slit produces discrete frequency noise (DFN) in certain conditions. It is known that their frequencies are coincided with those of the velocity fluctuation. In this study, air flow was induced by a blower. When the jet velocity from a rectangular slit (width: 20 mm, height: 2 mm, depth: 3 mm) was 19 m/sec the DFN had a peak frequency of 4.3 kHz intermittently. When a momentum was added to the jet flow in the vertical direction of it by the plasma actuator, however, the DFN was generated continuously. By smoke visualization technique a deflection of the jet flow to the direction of the added momentum was observed. It was considered that by activating the plasma actuator more vortexes were generated and velocity fluctuation occurred more frequently