Surface Integral Analogy Approaches to Computing Noise Generated by a 3D High-Lift Wing Configuration

Abstract

Three surface integral approaches of the acoustic analogies are studied to predict the noise from a three-dimensional, high-lift wing configuration. The approaches refer to the Kirchhoff method, the Ffowcs Williams and Hawkings method of the permeable integral surface and the Curle method. The first two approaches are used to compute the noise generated by the core flow region where the energetic structures exist. The last approach is adopted to predict the noise specifically from the pressure perturbation on the wall. A new way to construct the integral surface that encloses the core region is proposed for the first two methods. Considering the local properties of the flow around the complex objective -the actual wing with high-lift devices -the integral surface based on the vorticity is constructed to follow the flow structures. The noise from the core flow region is based on the dependent integral quantities, which are indicated by the Kirchhoff formulation and by the FWH formulation. The role of each wall component on noise contribution is analyzed using the Curle method. The results of the three methods are then compared.

Hybrid RANS/LES Simulations for Aerodynamic and Aeroacoustic Analysis of a Multi-Element Airfoil

“…A similar behavior was observed by Yao et al10 for high-lift wings without a leading edge slat. In the range of θ ≈ 210 • -330 • , p ′…”

“…(3a) and (3c)). Yao and co-workers 10 show that the noise due to term 3 behaves like a dipole with radiation roughly in the θ = 100 • and θ = 280 • directions. Only weak dipole trends with radiation maxima roughly in the θ = 80 • and θ = 240 • directions can be observed here, but it is likely that the present high-lift configuration with an additional slat behaves differently than the one investigated by Yao and co-workers.…”

“…In this formulation, the first and second integrals can directly be understood in physical terms as the loading and the thickness noise, respectively. 32, 41 When a permeable surface is used, the terms lose their physical meaning and it is hence legitimate to write them as individual integrals, as in Yao et al 10 In Eq. (6), it is then possible to interpret the three terms as the perturbations of pressure, momentum and mass through the surface, respectively,…”

“…6 More recently, numerical predictions were made using computational fluid dynamics (CFD). [7][8][9][10] Often only the near-field noise signature is investigated numerically, as in, 11 but some authors also computed the far-field noise. 7,8 It is now widely acknowledged that the slat in particular dominates the noise signature of typical highlift wings.…”

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“…The propagation of the sound from sources with arbitrary motions in subsonic constant free-stream flow is expressed in Equation (1). By adopting a permeable surface away from the solid body walls, this equation is capable of including the contributions of dominant quadruple sources that are located within this permeable surface [25]. The quadruple sources outside the permeable surface are neglected due to their minor contributions.…”