The aeroacoustics of a boundary layer ingesting (BLI) ducted fan is investigated experimentally. The study examines a ducted fan immersed in an adverse streamwise pressure gradient turbulent boundary layer developed over a curved wall. Aeroacoustics measurements indicate that the noise from the BLI ducted fan results from a complex interaction among the fan, duct and the incoming boundary layer. The fundamental mechanisms of noise generation are explained using a general source separation strategy. A detailed noise comparison is made at varying fan rotational speeds and across a wide range of axial inflow velocities. In a low thrust regime, the noise is found to be driven by the fan loading, coupled with duct acoustics and the haystacking phenomenon. In a high thrust regime, the contribution from duct acoustics diminishes, and the noise is predominantly driven by the fan loading coupled with the haystacking phenomenon.

中文翻译：

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吸收逆压梯度边界层的涵道风扇的气动声学

通过实验研究了边界层吸入 (BLI) 涵道风扇的气动声学。该研究检查了沉浸在弯曲壁上形成的逆流向压力梯度湍流边界层中的涵道风扇。气动声学测量表明，BLI 涵道风扇的噪声是由风扇、管道和传入边界层之间复杂的相互作用产生的。使用通用的源分离策略解释了噪声产生的基本机制。在不同的风扇转速和各种轴向流入速度下进行了详细的噪声比较。在低推力状态下，噪声是由风扇负载以及管道声学和干草堆积现象驱动的。在高推力状态下，管道声学的贡献减弱，噪声主要由风扇负载和干草堆积现象驱动。