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Numerical simulation of fore and aft sound fields of a turbofan

A framework for predicting fan related noise from high bypass ratio engines is presented. The methodology accounts for both fore and aft radiation and includes the effects of liner treatment on the engine walls. Solutions are obtained through a combination of Euler and linearized Euler solvers, coupled with a Kirchhoff formulation for far-field noise prediction. The nacelle region is solved using the Eider solver, whereas the linearized Euler solver is used for the fan exhaust stage. Switching to the linearized Euler solver in the aft region has been necessary to overcome difficulties experienced due to the coupling of the acoustic modes with flow near the engine exhaust boundary and appearance of flow instabilities in the shear layer trailing the exhaust shroud. Results are presented for spinning modes from a turbofan engine with acoustic treatment.