International Research Fellowship Program: Aeroacoustic Model for an Elastic Lifting Surface with a Soft, Sound Absorbant Coating: The Silent Flight of Owls

0965248Jaworski国际研究奖学金计划使美国科学家和工程师能够在国外进行九到二十四个月的研究。 该项目的奖项为联合研究以及使用国外独特或互补的设施、专业知识和实验条件提供了机会。该奖项将支持贾斯汀·贾沃斯基博士与贾斯汀·贾沃斯基博士一起工作的为期二十四个月的研究奖学金。英国剑桥大学的 Nigel Peake 和 Timothy J. Pedley。猫头鹰采用多种噪声抑制功能来降低猎物听力敏感度内的声学特征，其中大部分与人类听觉相同。 其中两个噪声抑制特征，即位于机翼某些区域的柔软纤维天鹅绒材料和弹性锯齿状后缘，被认为可以协同工作，减少背景湍流对噪声散射的影响，并在大频率带宽内消散声音。 尽管最近努力通过实验量化软涂层的气动声学效应，但目前尚不存在可行的理论模型。 本研究系统地解决了这些噪声抑制机制的气动声学影响，并将多孔介质声学的影响与天鹅绒涂层对流场的气动影响分开。 通过这种方式，所提出的研究结果可以直接与实验和最先进的气动声学计算进行比较。 每个猫头鹰噪声抑制机制都被简化为物理一致的模型，扩展了研究文献中的气动声学分析结果，最终为新颖的计算设计工具提供了通用且统一的气动和气动声学框架。 这项工作开发的设计工具和原理将使未来设计更安静的固定翼和扑翼微型飞行器（MAV）在类似于猫头鹰的流动状态下运行。 从这项研究中汲取的经验教训还可以为更高雷诺数和马赫数升力表面的降噪技术提供参考，包括功能性静音飞行器。

0965248JaworskiThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. Justin Jaworski to work with Drs. Nigel Peake and Timothy J. Pedley at the University of Cambridge in the UK.Owls employ multiple noise suppression features to reduce their acoustic signature within the hearing sensitivity of their prey, much of which is shared by human audition. Two of these noise suppression features, a soft, fibrous velvet material located at certain areas of a wing and an elastic, serrated trailing edge, are thought to work in concert to reduce the effect of background turbulence on noise scattering and to dissipate sound within a large frequency bandwidth. Despite recent efforts to quantify the aeroacoustic effect of a soft coating experimentally, a viable theoretical model does not currently exist. The present research systematically addresses the aeroacoustic impact of these noise suppression mechanisms and isolates the impact of porous media acoustics from the aerodynamic influence of the velvet coating on the flow field. In this manner, the results from the proposed research can be compared directly against experiment and state-of-the-art aeroacoustic computations. Each of the owl noise suppression mechanisms is reduced to physically consistent models that extend analytical aeroacoustics results in the research literature, culminating in a generalized and unified aerodynamic and aeroacoustic framework for a novel computational design tool. The design tool and principles developed from this work will enable quieter future designs for fixed and flapping wing micro air vehicles (MAVs) that operate in flow regimes similar to owls. Lessons learned from this research may also inform sound reduction techniques for lifting surfaces at higher Reynolds and Mach numbers including functionally-silent air vehicles.