Refraction Corrections for Surface Integral Methods in Jet Aeroacoustics

Abstract

One of the major challenges in computational jet aeroacoustics is the accurate modelling and prediction of acoustic flelds in order to reduce and control the jet noise. Surface integral methods (e.g. Kirchhofi method and Ffowcs Williams - Hawkings (FW-H) method) can be used in Computational Aeroacoustics (CAA) in order to extend the near-fleld CFD results to far-fleld. The surface integral methods can e‐ciently and accurately predict aerodynamically generated noise provided the control surface surrounds the entire source region. However, for jet noise prediction, shear mean ∞ow exists outside the control surface that causes refraction. The mean ∞ow refraction corrections had been done in the past using simple geometric acoustics (GA). A more rigorous method based on Lilley’s equation is investigated here due to its more realistic assumption of the acoustic propagation. Jet noise computational results based on Large Eddy Simulation (LES) for the near-fleld for an isothermal jet at Reynolds number 400,000 are used for the evaluation of the solution on the FW-H control surface. The proposed methodology for prediction of far-fleld sound pressure level shows that the acoustic fleld within the zone of silence is consistent with the experimental results.