Noise Prediction of the LAGOON Landing Gear Using Acoustic Analogy and Proper Orthogonal Decomposition

Azevedo, Paulo; Wolf, William

doi:10.2514/6.2016-2768

Cited by 2 publications

(1 citation statement)

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“…De Azevedo and Wolf 23 in their extensive landing-gear study separated not only the contributions of various parts of the solid surface, but also parts of the permeable surfaces, as well as many of the terms in equation (1). The permeable end-cap was dominant, which was a serious concern.…”

Section: Introductionmentioning

confidence: 99%

On the differences in noise predictions based on solid and permeable surface Ffowcs Williams–Hawkings integral solutions

Spalart

Belyaev

Shur

et al. 2019

International Journal of Aeroacoustics

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The Ffowcs Williams-Hawkings equation is widely used in computational aeroacoustics to postprocess unsteady simulations and provide the sound at distances beyond the accurate range of the grid. It distinguishes the monopole/dipole contributions from solid surfaces R and that from quadrupoles present in the volume of the fluid. Curle showed that at low Mach numbers, the solid-surface terms are stronger than the volume term. Very few studies have included the volume term itself, but many have used a permeable Ffowcs Williams-Hawkings surface R, which in principle surrounds the quadrupoles, giving valid results independent of Mach number; in reality for external flows, the surface cannot surround all the quadrupoles. However, in spite of doubts over the solid-surface approach even at low Mach numbers, it is widely used because of its simplicity and the difficulties associated with turbulence crossing the permeable surface. We consider Mach numbers M up to 0.25, which challenges approximations based on the property that "M (1." An additional attraction of the solid-surface approach is the idea of identifying the "true" source of the sound by computing separately the Ffowcs Williams-Hawkings integrals for different components. We wish to determine whether this "self-evident" argument gives an effective approach, and in general to assess Curle's approximations, using a sphere-dipole problem and three model problems related to landing-gear noise, namely an isolated rectangular body, a fuselage with a cavity, and one with a bluff body under it. One key test is the shielding of sound toward various directions;

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Section: Introductionmentioning

confidence: 99%