Abstract Aerodynamic noise generated by aerofoil-vortex interaction has widely been studied in the past where the primary noise source mechanism is the scattering of the vortex at the leading edge (LE) of the aerofoil. In this paper the secondary source mechanism – the subsequent vortical scattering at the trailing edge (TE) – is investigated in detail, which shows that this mechanism is essentially due to nonlinear effects as predicted by some analytical studies in the past. The present study is performed by employing high-resolution numerical simulations based on a prescribed non-singular vortex impinging on a flat-plate aerofoil with zero mean loading. The present work investigates both inviscid and viscous flow conditions. The inviscid flow condition is intended to support and extend from the existing theoretical works, whereas the viscous one leads to more realistic findings. The current viscous study involves laminar boundary layers and their convective instability travelling with the impinged vortex. One of the most notable observations made in this work is that the vortical scattering at the TE (in the absence of turbulent boundary layers) may become a dictating source of noise at high frequencies (surpassing the primary source at the LE) across a wide range of observer angles for both inviscid and viscous flow conditions. It is found that the high-frequency dominant source is produced by secondary near-wall vortices that are induced as a result of nonlinear interactions between the aerofoil and the impinging vortex. This new discovery makes a contrast to the existing knowledge on aerofoil-vortex interaction noise in which the secondary source is normally assumed inferior to the primary at all frequencies.

中文翻译：

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平板机翼与指定涡旋相互作用产生的后缘噪声

摘要 翼型-涡流相互作用产生的气动噪声过去得到了广泛研究，其中主要噪声源机制是翼型前缘（LE）处涡流的散射。在本文中，详细研究了二次源机制——后缘 (TE) 处的后续涡旋散射，这表明这种机制主要是由于过去一些分析研究预测的非线性效应。本研究是通过采用高分辨率数值模拟进行的，该模拟基于规定的非奇异涡流撞击平板翼型，平均载荷为零。目前的工作研究了无粘性和粘性流动条件。无粘性流动条件旨在支持和扩展现有的理论工作，而粘性的会导致更现实的发现。当前的粘性研究涉及层流边界层及其随撞击涡流传播的对流不稳定性。这项工作中最值得注意的观察结果之一是，TE 处的涡旋散射（在没有湍流边界层的情况下）可能会成为大范围内高频（超过 LE 处的主要噪声源）的决定性噪声源无粘性和粘性流动条件下的观察者角度。结果表明，高频主源是由机翼和撞击涡流之间非线性相互作用引起的次生近壁涡流产生的。