Noise Control of a High Reynolds Number High Speed Heated Jet Using Plasma Actuators

Abstract

Localized arc filament plasma actuators (LAFPAs) have been used to control the flow and far-field acoustics of high Reynolds number, high-speed unheated jets at the Gas Dynamics and Turbulence Laboratory. The jet facility consists of an axisymmetric jet of exit diameter 2.54 cm with different nozzle blocks and variable jet temperature in an anechoic chamber. The focus of this paper is on the effect of control on far-field noise in a high subsonic ( Mj = 0.9) jet over a wide range of temperatures. A total of sixteen combinations of forcing azimuthal modes ( m = 0, 1, 3, and ±4) and temperature ratios ( To/ Ta = 1.0, 1.5, 2.0, and 2.5) at a wide range of forcing frequencies were utilized to explore LAFPAs' effect on far-field noise. LAFPAs show significant noise reduction around the peak frequency in shallow angles and a small increase in higher frequencies. The level of reduction is lower and the level of increase is higher towards the sideline. Consistent with previous works, the results show that forcing with higher azimuthal modes produces greater noise reduction. LAFPAs produce large amplitude narrowband tones in this small jet that are believed to be less significant in larger jets. The impact of these forcing tones is isolated and discussed. Across the range of temperatures explored, the effectiveness of LAFPAs improves as temperature increases. Possible reasons for the increase in effectiveness are discussed.