Leading-Edge Noise Prediction of General Airfoil Profiles with Spanwise-Varying Inflow Conditions

Abstract

This paper presents a study of the leading-edge noise radiated by an airfoil undergoing a turbulent inflow. The noise prediction of generic airfoil profiles subjected to spanwise-varying inflow conditions is performed with the support of Amiet's theory and the inverse strip technique. In the proposed methodology, the aeroacoustic transfer function of a generic airfoil profile is computed by the boundary element method. The effects of the airfoil leading-edge thickness on the inflow turbulence are accounted for by a turbulence spectrum based on the rapid distortion theory. This research shows that the turbulence distortion plays a significant role on the predicted noise levels. Compared with the von Kármán model for isotropic turbulence, the rapid distortion theory predicts reduced noise levels at high frequencies and increased noise levels at low frequencies. This paper also shows that the spanwise-varying inflow, here represented by a linearly changing condition, contributes to raising the noise levels when compared to the similar uniform inflow case. This research confirms that the finite airfoil thickness decreases the airfoil-gust lift response, consequently reducing the noise levels. This observation is more pronounced for microphones positioned downstream of the airfoil and for high frequencies.

Rapid distortion theory of turbulent flow around a porous cylinder

“…Christophe (2011), de Santana (2015), de Santana et al. (2016) and Miotto, Wolf & de Santana (2018) employed a similar correction to model the upstream two-dimensional turbulence spectrum as input to Amiet's theory by considering the asymptotic results for small-scale turbulence and by assuming the conservation of the variance of the velocity fluctuations. Likewise, this methodology resulted in improved noise predictions compared with Amiet's original formulation.…”

Challenges and opportunities for low noise electric aircraft

“…118–120 Rapid distortion theory (RDT) 121,122 is often used to determine how turbulence is affected by irrotational mean flows, and the resulting effects on noise. 116,118–120,123,124…”

“…These effects have been studied using a variety of analytical 113,116,117 and numerical methods, 117 such as the boundary element method (BEM) and panel methods. [118][119][120] Rapid distortion theory (RDT) 121,122 is often used to determine how turbulence is affected by irrotational mean flows, and the resulting effects on noise. 116,[118][119][120]123,124 The effects of non-uniform mean flow upstream of the airfoil represent another important extension to Amiet's work.…”

Influence of geometric structure, convection, and eddy on sound propagation in acoustic metamaterial with turbulent flow

“…Turbulence effect of the fuselage on the fan noise of the BLI (Boundary-Layer Ingestion) configuration [16], the relationship between the structural flexibility of the elastic trailing-edge and the aeroacoustic response [17], prediction of broadband sound generated in a low Mach number turbulent boundary layer by lattice Boltzmann method (LBM) [18], simulation of indoor noise generated by indoor window vibration [19], and acoustic source model to reduce aerodynamic noise generated from wind turbine blades [20] have been discussed. Most of the interest, such as the reduction of aerofoil interaction noise by new serration profile group [21,22], the noise generation mechanism of controlled diffusion aerofoil and their dependence on Mach number [23], and the role of the porous material placed on the tail edge of the 3D chamber airfoil [24], focuses on the reduction of noise caused by the interaction between aerofoil and turbulent flow.…”