A fast prediction method for rotor buzz-saw noise based on an analytical approach

The present work proposes a time-domain two-dimensional radial-strip approach for the fast prediction of buzz-saw noise that is emitted by supersonic and transonic rotors. The first part of the paper gives an overview on existing prediction models related to this problem and motivates the need for an extended analytical prediction including the properties of the shocks at their generation. The fan application considered to validate the model is also presented in this part, as well as the numerical set-up of the quasi-3D RANS simulations to be compared with the model. In the second part, the analytical model is first established for the case where all blades are identical. In this part, two new relations for the initial shock strength and the initial shock positions are presented. Their domain of application extends from the subsonic to the supersonic regimes. Finally in the third part of the paper, the model is extended to the more general case with non-identical blades. A new model correlating analytically the blade angle deviations with the individual shock positions is derived and discussed. It is shown that despite strong assumptions, the analytical predictions are able to reproduce properly the main results obtained from the RANS simulations.