Analytical model for predicting rotor-stator interaction tonal noise in low-speed axial fans

Analytical models for aeroacoustic simulations are valuable due to their potential to reduce computational costs, a crucial consideration to optimize noise performance. Analytical models proposed so far focus mainly on isolated steady and unsteady fan tonal noise, often neglecting the significant contribution of rotor-stator interaction. As a matter of fact, for short axial spacing, tonal noise from potential flow interactions is relevant. This study presents an analytical model for predicting rotor-stator interaction noise caused by the stator vane potential effect on blades. The model requires only time-averaged flow fields from URANS simulations with periodic boundary conditions. Key features include accounting for uneven spacing and arbitrary chord, twist, and sweep distributions of blades and vanes. The model is based on the Sears aerodynamic model for blade loading fluctuations and the time-domain Ffowcs Williams-Hawkings formulation for noise prediction. Validations with evenly and randomly spaced blade show the model capability to predict tonal noise trends. The model captures noise at the blade passing frequency and harmonics associated with rotor-stator interaction. The model fails to predict noise at higher harmonics due to trailing edge noise sources, not currently accounted for. Future works will extend the model to broadband noise sources.