Quasi-compact model for accurate noise prediction of complex rotor configurations

The design of urban air mobility systems requires fast yet accurate aerodynamic and acoustic analyses of propeller interactions. Low-fidelity solvers relying on compact F1A formulations are commonly used, but the compact acoustic assumption does not hold for loading noise produced by unsteady inflows. This study introduces a quasi-compact acoustic model applied to isolated and tandem interacting propellers comparing its performance against other hybrid solvers. The quasi-compact model propagates the local chord-wise and span-wise pressure jump distribution computed with a non-linear vortex-lattice aerodynamic solution to far-field observers. Compact models simplify this by using the span-wise distribution only. Reference solutions are generated by propagating high-fidelity CFD pressure fields to far-field observers using the same Ffowcs Williams-Hawkings solver. Results demonstrate that the compact formulation achieves convergence only for isolated propellers, whereas the quasi-compact formulation can provide converged solutions also with rotor-rotor interactions and compares better with the reference high-fidelity data.