Computation of free-jet turbulence and exhaust-mixing noise from a turbofan engine

A model presented previously [D. B. Schein, paper 3pEA3, 136th Meeting of ASA (1998)] has been extended and applied to prediction of exhaust noise from a high Reynolds number, hot exhaust flow. Simulations for a Williams Research WR19-4 turbofan engine exhaust have been performed and results compared with far-field acoustic data measured during static test runs of the engine at exhaust Mach numbers up to 0.8. The hybrid CFD/CAA approach employs a deductive subgrid scale model for small-scale compressible turbulence combined with the time-derivative form of Lighthill’s source-integral acoustic analogy, containing the fluctuations represented by the time-varying stress tensor. Overall sound pressure level directivity and representative spectra are presented. Analytical results indicate generally good agreement with measured data and popular semiempirical prediction methods. Spectral analysis indicates that significantly larger computational domains and simulation times will be required to obtain low-frequency energy content radiated from aircraft engine exhausts.