Time Domain Measurement and Prediction of Propeller Noise Due to Locally Distorted Inflow

This paper presents both experimental and numerical analyses of blade interaction noise due to locally distorted inflow in time domain. The locally distorted inflow is generated by upstream of rotating propeller combined with a small jet and the far-field noise has been measured, changing speed of the jet. Notably, impulsive waveform characteristics in the far-field noise measurements were identified, which could increase overall sound pressure level. To understand the characteristics of distortion noise and estimate its level, two-dimensional numerical models focusing on the gust response and far-field radiated sound pressure in the time domain have been investigated. The gust response has been obtained with Amiet's solution for a delta-function type of gust convolved with the measured distorted flow. This approach enables the prediction of radiated noise. Finally, a comprehensive comparison between predicted sound pressure and acoustic measurement is investigated and discussed.