Aeroacoustics investigation of the noise from an asymmetric nozzle

Aircraft noise emissions reduction has become a driving factor for competitive aircraft design as environmental laws have become stricter. Moreover, the design of future aircraft, both subsonic and supersonic, is strongly dependent on the development of novel noise reduction designs. Hence, commercial turbofan engines and military aircraft engines require innovative jet noise reduction concepts. One such is the use of asymmetric nozzles. In this paper the authors present numerical simulations of the flow field and the noise generated by an asymmetric nozzle. The objective of this study is to test the application of the novel noise prediction method called LRT, which is a fast RANS-based methodology that includes flow/sound interaction, to an asymmetric nozzle for different operational conditions. Investigations are conducted to gain insight into the flow characteristics and sound propagation that yield a noise modification in the far-field when compared to a baseline symmetric nozzle. Results from both RANS and noise computations are presented. Experimental results for the far-field noise are compared against the LRT predictions showing the ability of the method to predict the noise from 3D nozzles. The results are encouraging and this study is part of an on-going effort to better understand the flow dynamics and its interaction with noise propagation to possibly develop a more silent nozzle concept.