The effect of flow circulation on the scattering of landing gear noise

Abstract

An investigation into the scattering of landing gear noise sources by a lifting wing is presented. A two-dimensional test case is used in the investigation. The noise sources are represented by a monopole, which is located at the approximate position of a landing gear underneath a wing geometry. A linearized Euler equation solver is used to simulate the scattering of the monopole by the wing. The effect of a non-uniform flowfield due to circulation induced by a lifting wing is quantified as the difference in acoustic scattering over uniform and non-uniform base flows. The results show that increasing the angle of attack, or increasing the Mach number, leads to a small increase in the sound pressure level towards the ground. However, the observed increase is relatively small. A boundary element method solver is then used to investigate the same problem, and existing uniform and non-uniform flow boundary element formulations are evaluated to see which more accurately predicts the effect of flow. The results show that the uniform flow boundary element formulation is more accurate in predicting the effect of flow than the non-uniform flow approximation for this particular problem, and that the extra computational effort required for the non-uniform flow approximation does not yield a more accurate result.

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