Modification of Amiet's model for turbulence-ingestion noise prediction in rotors

Amiet’s model for turbulence-ingestion noise prediction for rotors is adapted to incorporate pointwise velocity mea- surements as input. This is accomplished by using an inverse strip theory approach and transforming the three- dimensional turbulence spectrum, which models inflow conditions, into a one-dimensional term. This latter modifica- tion enhances the low-fidelity prediction tool in two key ways. First, it enables its application in cases where turbu- lence modeling is unavailable, or detailed inflow characterization is impractical. In this way, for example, hot-wire anemometry measurements of the incoming turbulence can be used to compute the acoustic prediction. Second, since the conversion of the turbulence term entails introducing two new functions describing spanwise and axial turbulence correlations; this approach establishes a framework for Amiet’s theory in which the contributions to turbulence alter- ation and noise scattering are separated and represented individually. This “modular” structure enables independent analysis and modeling of these contributions, facilitating the application of Amiet’s model to complex flow configu- rations and rotor geometries. The proposed methodology is successfully validated through experimental measure- ments of a simplified axial-flight turbulence-interaction setup, where a two-bladed propeller interacts with grid- generated turbulence at three different advance ratios.