Numerical investigations of tonal noise of counter-rotating open rotors

In the work are presented the results of a three dimensional computational analysis of tonal noise of two counter-rotating open rotors. The analysis was performed using 3DAS (3 Dimensional Acoustics Solver) CIAM in-house solver, designed for three dimensional calculation of turbomachinery tone noise generation, propagation and radiation in the near and the far acoustic fields. The results of the computations were compared with the results of experiments performed in the wind tunnel of Central Aerohydrodynamic Institute (TsAGI), Russia, within the project DREAM (Validation of radical engine architecture systems) of European Seventh Framework Programme (FP7). The comparison showed satisfactory correspondence between directivity diagrams for the tone noise on combinational harmonics.