Characterization of Installation Effets for HBPR Engine Part IV: Assessment of Jet Acoustics

This paper is the last part of a series of four papers characterizing the installation effects of a typical high bypass ratio engine jet using numerical simulations and particle image velocimetry. The global objectives are an improved understanding of the link between the jet flows and the generated noise, the validation of methods for computing the aerodynamic field and the noise sources for industrial configurations, and the assessment of the benefits of a serrated nozzle when installed under a wing profile. This paper proposes an evaluation of the jet acoustics of under-wing nozzles with experimental and numerical tools. Far-field and near-field noise is measured in the CEPRA19 anechoic facility. Acoustic maps of jet noise sources are obtained using a beamforming technique. Characteristic effects of jet velocity and flight simulation are observed on measured jet noise in the near-field and far-field, and are related to the flow-field analysis. CFD-CAA tools are able to capture the effect of flight on jet mixing noise. The low-frequency source peak is located by beamforming on experimental data in the region of intense mixing downstream of the nozzle pylon. The cross-analysis with CFD, PIV data and numerical tools confirms that the pylon plays a major role in mixing noise signature. The serrations are found to have a peculiar behavior