Influence of viscosity on entropy noise generation through a nozzle

Entropy (temperature) fluctuations produced by turbulent flames generate noise when they are accelerated the flow. This so-called entropy is an important contributor to core in modern aeroengines and several semi-analytical models exist literature for its prediction. All these assume flow be inviscid. In present paper, contribution of viscosity on generation scattering through a nozzle investigated numerically with URANS simulations analytically extension 2D inviscid model Emmanuelli et al. (2020). Simulations indicate slightly reduced medium-frequency range presence variations below 3 dB comparison reference data. variation qualitatively well reproduced low-order model. The major effect propagation lies boundary layers. Viscous sources viscous diffusion acoustic perturbations have negligible impact noise. Discrepancies between analytical solutions found come from radial evolution waves thick layers, not accounted model, which scattering.