Effects of Shear Layer Characteristics on Acoustic Propagation and Source Localization

Abstract

The shear layer characteristics of an open-jet acoustic wind tunnel are of key importance on measurements of aeroacoustics. The effects of thickness, spreading angle and strength of shear layer on acoustic propagation and source localization are investigated through the mean/spreading shear layer with a self-similar velocity distribution. Based on the shear flow, the acoustic propagation is computed by the linearized Euler equations via a source term, and then source localization is obtained from beamforming technique combined with the theory of Amiet. Results show that the numerical method can precisely capture the refraction and reflection after sound traversing shear layer. The thickness, spreading angle and strength of the shear layer exerts little effects on the refracted region where sound wave nearly vertical incident, while mainly influence the corresponding up/downstream region in terms of phase change. Increment of thickness, spreading angle and strength of the shear layer increases the acoustic difference between the shear layer with and without thickness, and produces a larger error of source localization downstream of the actual position.

Numerical study on the noise propagation characteristics of rotor in non-uniform downwash flowfield Based on Linearized Euler Equations

“…To research the rotor noise propagation characteristic in non-uniform downwash flowfield, it is necessary to verify the computational aeroacoustics code in a non-uniform flowfield. Because the kernel of the two-dimensional CAA code is the same as the three-dimensional CAA code, the two-dimensional problem of the monopolar source in a sheared mean flow 38,53 is adopted to verify the CAA code.…”

“…9,10 Wang L et al investigated the effect of hot jet flow on acoustic propagation by solving linearized Euler equations. 26,38,39 Jiao et al studied the shear layer effects in both 2D and 3D sound propagation by solving linearized Euler equations or acoustic perturbation equations. 40 Most of the work are carried out with elementary noise sources.…”