Prediction of turbulence-cascade interaction noise using modal approach

The turbulent wakes generated by a rotor interacting with outlet guide vanes is one of the dominant broadband noise sources in a turbofan engine. The present paper deals with the prediction of broadband noise due to the interaction of rotor wake turbulence with the OGV. The proposed approach aims to reproduce the two-point cross-spectral statistics of the turbulent velocity fluctuations at the OGV leading edges, which provides a complete specification of the rotor wake turbulence for broadband noise predictions. The approach proposed here is based on a superposition of vortical modes with the appropriate amplitudes. Three different vortical modes are compared for their reconstruction efficiency and accuracy: 1) Fourier modes, 2) Proper Orthogonal Decomposition (POD) modes 3) Normal modes of the Linearized Euler Equations (LEE).