CFD Analysis of Buzz Saw Noise Employing Time-Domain Non-Linear Impedance Boundary Conditions

Abstract

Buzz saw noise emerges in turbofan engines featuring supersonic blade tip speeds and perturbed blade loadings. Such conditions occur at high-power climbing operations and result in considerable noise emissions. This paper employs Computational Fluid Dynamics (CFD) simulation to illustrate the non-linear interaction between the buzz saw noise generating mechanism and acoustic liners in a generic UHBR engine. Blade loading perturbations are modeled by applying blade twist deviations. Additionally, a newly developed time-domain non-linear impedance model is introduced as a boundary condition to incorporate the effects of acoustic liners. The study investigates the impact of both applied twist deviations and liners on the resulting buzz saw noise spectrum. The results demonstrate the capability of CFD simulation to accurately model buzz saw noise. Future research should focus on validating these results, improving the dynamics of the liner model, exploring the benefits of non-uniform liner design, and investigating aeroelastic interactions with liners.