Investigation of Noise Sources in Turbulent Hot Jets Using Large Eddy Simulation Data

Abstract

Through the use of Lighthill’s acoustic analogy, the aim of this paper is to investigate the noise sources of turbulent heated round jets using previously simulated Large Eddy Simulation (LES) data. Two heated and one unheated jet are considered to study the e ects of heating on the noise source contributions to the far-field. Firstly, the computed overall sound pressure level (OASPL) and spectra are in good agreement with the prediction obtained from the porous Ffowcs Williams-Hawkings (FWH) surface integral method. Like the FWH prediction, however, the computed OASPL over-predicts the experiments by approximately 3dB but the trends agree reasonably well with the experimental results. Through decomposition of the Lighthill source term we obtain such sources as shear, self and entropy noise. An important finding is that when a high speed subsonic compressible jet is heated while keeping the ambient jet Mach number constant, significant cancellations occur in the far-field between the shear and entropy noise. In addition, heating a jet reduces the intensity of the nonlinear self noise terms compared to an unheated jet. For a low speed heated jet, the main contributing source is the entropy noise source while the shear and self noise sources hardly contribute to the far-field noise.