Aeroacoustics of a Rotor in Forward Flight Using an Advanced Lifting-Line Model

This work presents the aeroacoustic results of an advanced unsteady lifting-line theory (ULLT) predicting rotor noise in forward flight. The method couples a time-domain Kussner–Schwarz aerodynamic model, a rational approximation of unsteady circulatory effects, and a free-wake algorithm to generate harmonically rich sectional loads at low computational cost. A reduced-frequency scaling tailored to rotary-wing motion ensures accurate local unsteady modeling. The approach is assessed on a BO105 scaled main rotor, showing close agreement with experimental and simulation reference data for both rotor loading and wake-driven high-frequency content. Acoustic pressures obtained via the compact Farassat 1A formulation reproduce the dominant loading-noise signatures with consistent amplitude and phase. Results demonstrate that the enhanced ULLT framework provides an efficient and physically consistent tool for rotor aeroacoustic prediction, well suited to early-stage design and optimization.