Application of a 2.5D harmonic balance method to a calculation of unsteady disturbances propagation through a duct of a turbofan

The method of calculation of tone noise propagation through a duct of turbomachine, taking into account nonlinear effects, is presented. It is based on the decomposition of the solution on the set of circumferential modes and performing the calculations for the complex amplitudes of this modes using harmonic balance approach. The usage of the method can lead to an acceleration of simulations of noise propagation through inlets and nozzles of turbofans in the cases when the nonlinear effects cannot be neglected. The method is implemented in the CIAM 3DAS (3 Dimensional Acoustics Solver) in-house solver. It was verified on the problem of nonlinear interaction of circumferential modes in 2D cylindrical channel. The results of the calculation, performed using the method, showed satisfactory correspondence with the results of the time domain calculation.