Analysis of blade noise with different root boundary conditions considering fluid-structure interaction effect

Abstract

It is of certain importance for noise reduction to investigate the relationship between the aeroacoustic characteristics of blade and root boundary conditions when considering the FSI (Fluid-Structure Interaction) effect. In this study, a set of precise dynamic models and two-way FSI calculation methods are developed to predict the dynamic load and response of blades more accurately. The natural frequency inaccuracy of the blade model is kept within 5% by comparing the results of the modal test using the PTD(Ploy-reference Time Domain) method and adopting the sensitivity analysis method with the blade beam stiffness as the modification parameter. Besides, based on the numerical results from the CFD(Computational Fluid Dynamics) method considering the FSI effect , the aeroacoustic characteristics of blades with different root boundary conditions are analyzed by adopting the FW-H (Ffowcs Williams-Hawkings) equations. The aeroacoustic characteristics of the NACA blade in hover are thoroughly discussed, with emphasis on the impact of different root boundary conditions on rotation noise. The result demonstrate that, the SPL(Sound Pressure Level) difference of loading noise can reach 1.4dB between blades with various root boundary conditions, while the SPL difference of thickness is only 0.4dB.