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

0965248 Jaworski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9到24个月的研究。该项目的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持贾斯汀·贾沃斯基博士与英国剑桥大学的奈杰尔·皮克博士和蒂莫西·J·佩德利博士合作，为期24个月的研究奖学金。猫头鹰采用多种噪音抑制特征，以降低其猎物的听觉敏感度，其中大部分由人类听力共享。其中两个噪声抑制功能，位于机翼特定区域的柔软纤维天鹅绒材料和弹性锯齿状后缘被认为协同工作，以减少背景湍流对噪声散射的影响，并在较大的频率带宽内消散声音。尽管最近努力从实验上量化软涂层的气动声学效应，但目前还不存在可行的理论模型。本文系统地研究了这些噪声抑制机制对气动声学的影响，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隔离开来。通过这种方式，建议的研究结果可以直接与实验和最先进的空气声学计算进行比较。每个OWL噪声抑制机制都被简化为物理上一致的模型，这些模型扩展了研究文献中的空气声学分析结果，最终形成了一个通用的、统一的气动和气动声学框架，用于一种新的计算设计工具。根据这项工作开发的设计工具和原理将使固定和扑翼微型飞行器(MAV)在类似于猫头鹰的流态下运行的未来设计变得更加安静。从这项研究中学到的经验教训也可能为高雷诺数和马赫数升力表面的降声技术提供参考，包括功能上无声的飞行器。

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.