A Review of Turbomachinery Noise: From Analytical Models to High-Fidelity Simulations

Abstract

To address the need for noise predictions of any rotating machine, two different approaches are presented: fast-running analytical models as pre-design tools, and numerical methods to provide detailed analysis and physical insight in the noise sources. For both, a methodology in three steps is proposed, which includes the definition of the excitation, the blade response, and the propagation of the equivalent noise source to the far-field. For all machines, the excitation can be either vortical or acoustic gusts, and the far-field propagation is provided by an acoustic analogy either in free field or in a duct. Only the second step is either an isolated blade response for low speed ventilators or a cascade response for high-speed turbomachines. Overall, analytical models are shown to provide good and fast first sound estimates at pre-design stages, and to easily separate the different noise sources. On the numerical side, for all machines, unsteady Reynolds-Averaged Navier-Stokes simulations are shown to yield accurate tonal noise of the most complex configurations. Wall-modeled Large Eddy Simulations can provide the broadband noise part over most rotating components with good overall sound power level predictions. An accurate and efficient alternative to yield both contributions at once appears to be the hybrid Lattice-Boltzmann/Very Large Eddy Simulations.