Leading edge noise from thick foils in turbulent flows

Abstract

The prediction of dipole sound from the diffraction of turbulence by the leading edge of a rigid foil is made using acoustic analogies for homogeneous flows with and without mean shear. The Green’s function accounts for the foil thickness and leading edge shape. A comparison between the theory and published measurements suggests that the foil thickness exponentially attenuates the dipole sound pressure power spectrum by the product of the convection wavenumber and half the maximum section thickness. The ratio of the predicted dipole sound from the mean shear source to the source without mean shear is determined to be proportional to the ratio of the mean shear to the frequency of the sources.

Statistical–Empirical Modeling of Airfoil Noise Subjected to Leading-Edge Serrations

“…Note that the SPL for the serrated LE is shifted by 30 dB.The Amiet model[21] was also used to validate the AGI noise produced by a baseline, straight LE airfoil in the current setting. The Amiet's model was modified slightly by taking into account of the consideration of the airfoil thickness according to Gershfeld[22]:(4) where Λ uu is the longitudinal integral length scale of the turbulence, Tu is the turbulence intensity, R is the observer distance, b the airfoil semi-span, d is the airfoil thickness and is the normalized longitudinal wavenumber. The Λ uu and Tu were measured independently.…”

Asymptotic Approximations for the Sound Generated by Aerofoils in Unsteady Subsonic Flows

“…for large k. For r 1, we see f (r, θ s ) ∼ r 2 ∼ cos θ r , which is physically sensible because the far field sees a dipole source created by the body (Gershfeld 2004), and this yields…”

Stochastic modelling of leading-edge noise in time-domain using vortex particles

“…Gershfeld [24] developed a correction factor accounting for thickness in Amiet's flat plate model. Posson, Moreau, and Roger [26] extended Glegg's [27] analytical model of the aeroacoustic response of a rectilinear cascade of flat-plate blades to three-dimensional incident vortical gusts, to the prediction of the noise generated by a three-dimensional annular blade-row.…”

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