Low frequency broadband noise radiated by highly skewed propeller ingesting inflow turbulence

Low frequency broadband noise radiated by highly skewed propeller caused by inflow turbulence is numerically studied. In the first place, the broadband thrust spectrum acting on the blade surface is computed based on the strip theory. Once the thrust is obtained, pressure spectrum of noise resulting from the broadband force (force sources) and vibrations of blades (velocity sources) are computed separately. When computing noise radiated by the force sources, the blade surfaces are simplified as distributed dipole sources. When computing noise radiated by the velocity sources, three steps are applied as followed: Firstly, a simplified propeller-shafting system is established. The impedance function of each exciting node on the blade surfaces is formed based on the FEM model. In the second step, the random vibrations of the blades are calculated by multiplying the impedance function matrix with the thrust spectrum matrix. Finally, noise radiated by velocity sources is computed with the solutions of wave equations. On the basis of the numerical results, the radiated noise power of force sources and velocity sources are compared. The relationships of the modal characteristics and the radiated noise are discussed. Furthermore, the influences of inflow condition on the radiated noise level are discussed. The results and analysis may be helpful for the low-frequency vibration and noise reduction of the propeller. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study focuses on the low-frequency broadband noise radiated by highly skewed propeller due to inflow turbulence. By calculating the thrust spectrum, pressure spectrum, and analyzing the radiated noise power of force sources and velocity sources, the relationship between modal characteristics and radiated noise, as well as the influence of inflow conditions on noise level, are discussed for potential reduction of propeller vibration and noise.