Methods for the prediction of blade-vortex interaction noise

This paper compares aeroacoustic methods for the prediction of parallel bla de-vortex interaction noise using data from a specialized rotor test. The t est, performed in the NASA Ames 80- by 120-Foot Wind Tunnel, involved a sma ll-scale rotor interacting with a vortex generated by a wing mounted upstre am. These data were the focus of a working group that compared a wide range of methods for the prediction of BVI noise. The aerodynamic models include computational fluid dynamics, boundary element, and indicial methods. Acou stic methods include Kirchhoff methods and the Ffowes-Williams Hawkings app roach. The comparisons of computed and measured surface pressure data revea l a number of differences, none of which seem to have major acoustic signif icance. Comparisons of computed and measured far-field pressures show that BVI acoustics is generally well predicted when the blade aerodynamics are w ell defined, with more variations being found between the Kirchhoff methods . Within the limitations of the present test, this indicates that BVI noise is reasonably well predicted when vortex parameters (location, circulation , and core radius) are accurately known.