Aeroacoustic sources analysis of wake-ingesting propeller noise

Abstract

High resolution aeroacoustic source analysis is a prerequisite to address the noise concerns and release the full benefits of wake-ingesting propellers. In this work, the aeroacoustic sources of a two-bladed propeller ingesting the wake of an aerofoil are investigated using large eddy simulation in conjunction with two different source identifying approaches. The first approach is the numerical beamforming that utilizes both the classical and wavelet-based beamforming techniques, which determine the phase variations of sources at the low to mid frequencies and reveal that the high-frequency sources are phase-independent. To further improve the spatial resolution of source identification, a new near-field aeroacoustic source analysis approach based on the acoustic analogy is developed in this work. In particular, the on-surface source terms emanating the far-field noise are derived based on the Ffowcs Williams and Hawkings equation for low Mach number flows and constant rotating propellers. Through the incorporation of the simulation results into the proposed source analysis approach, various types of aeroacoustic sources are identified and studied by visualizing their distributions on the propeller surfaces, correlating to flow features and examining the noise spectra and directivity. While the leading edge sources are highly correlated with the wake interaction process, the sources at the mid-chord and the trailing edge of the blade can maintain their strength across most revolving angles. Overall, the proposed analysis approaches extend the capability of computational fluid dynamics and enable the detailed study of noise generation mechanisms of wake-ingesting propeller noise.

A high-intensity low-frequency acoustic generator based on the Helmholtz resonator and airflow modulator

“…In the 1960s and 1970s, Meyer [8] studied the acoustic principle of modulators. With the development of fluid mechanics, computational mechanics, and computer science, the theoretical simulation of the acoustic generation process of the aerodynamic acoustic source can be carried out [10][11][12][13][14][15]. Due to the complexity of the acoustic wave generated by the fluid, the theoretical simulation may not apply to various working conditions that generate acoustic waves.…”

Research on the Aerodynamic Noise Characteristics of Heat Exchanger Tube Bundles Based on a Hybrid URANS-FWH Method

“…Varying mirror inclination angles not only impact the drag coefcient nonlinearly but also infuence noise levels. Yangzhou et al [16] investigate the aeroacoustic sources of a two-bladed propeller in an aerofoil wake using large eddy simulation and FWH equation. A novel near-feld aeroacoustic source analysis based on the acoustic analogy is introduced, identifying various sources and correlating them with fow features, propeller surfaces, and noise spectra.…”

Theoretical research on the application of impedance calculation in the design of high-intensity low-frequency acoustic generator

“…Yang et al 8 simulated the acoustic source region of the helicopter rotor High-Speed Impulsive (HSI) noise by solving Navier–Stokes equations, and the acoustic near-field is simulated by solving the Linearized Euler Equations (LEE) based on the Runge–Kutta Discontinuous Galerkin (RKDG) method. Yangzhou et al 9 derived the on-surface source terms of the aeroacoustic sources of a two-bladed propeller emanating the far-field noise based on the Ffowcs Williams and Hawking’s equation for low Mach number flows and constant rotating propellers. Zhang et al 10 conducted a noise reduction study of an airfoil with a bioinspired ridge-like structure.…”