Numerical investigation of tone noise of a scale-model fan with ultra-low tip speed at cutback and sideline operational conditions using a method of calculation in frequency domain

Results of numerical investigation of tone noise of a scale-model fan with ultra-low tip speed at cutback and sideline operational conditions are presented. The investigation is performed using a method of calculation in frequency domain, developed in CIAM. An interaction between rotor blades and stator blades is taken into account. The fields of the flow pulsations in the near field and the distributions of sound pressure levels in the far field are obtained for both operational conditions. The data were compared with the results of the experiment conducted in the CIAM test rig. Satisfactory agreement between the results of the simulation and the experiment is shown. Qualitative similarity between the directivity diagrams obtained on the bases of computational and experimental data is observed. The dominance of the tone noise radiated from the nozzle in the tone noise of the fan is shown. Comparison of the obtained results with the results of the calculation of tone noise of a fan with supersonic tip speed is performed. Qualitative difference between directivity diagrams of tone noise for two different types of fans is shown. It is found out, that the reason of it is the noise of rotor rotation of the fan with supersonic tip speed.