Collaborative Research: Aerodynamic-aeroacoustic performance of poroelastic wings inspired by the silent plumage of owls

猫头鹰是一种非凡的捕食者，在攻击猎物/食物时能够抑制噪音并实现无声飞行。人们认为猫头鹰翅膀上的条纹图案有助于它们安静地飞行。了解猫头鹰翅膀上气流的物理特性可能有助于降低许多工程设计中的噪音，例如计算机风扇、推进器、商用飞机机体和风力涡轮机。本项目的主要目的是分析一系列的解析和数值模型问题，并结合实验测量来阐明具有与猫头鹰翅膀相当的梯度孔隙弹性的薄流体加载结构的非定常加载和噪声产生。该项目通过一个互动的理论-实验项目解决了上述技术缺陷，该项目在不少于三方面脱颖而出：(i)构建分析和数值框架，从第一性原理预测梯度多孔弹性结构产生的湍流噪声；（ii）无背景流噪声的孔隙弹性边缘声学标度规律的实验验证；（三）开发一种滑翔机来测量飞行时的翅膀噪音，这种方法与猫头鹰听到自己的噪音的方式一致。建模和验证工作旨在将生物噪声解决方案转化为低速流动被动气动噪声控制的合理范例，并为未来仿生猫头鹰降噪研究创建一个实验平台。该项目还将包括与达芬奇科学中心（Allentown， PA）的K-12教育推广，以及通过里海生物系统动力学暑期研究所（与北安普顿社区学院合作）整合本科生的研究参与，并通过里海和宾夕法尼亚州立大学之间的设计-建造-苍蝇竞赛。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Owls are extraordinary predators that are able to suppress their noise and achieve silent flight while attacking prey/food. The wing fringe pattern of owls is believed to contribute to their quiet flight. An understanding of the physics of the flow over owl wings may lead to noise reductions for many engineering designs, such as computer fans, propulsors, commercial airframes, and wind turbines. The principal aim of this project is to analyze a series of analytical and numerical model problems coordinated with experimental measurement to elucidate the unsteady loading and noise generation of thin fluid-loaded structures with graded poroelastic properties comparable to owl wings. This project addresses the above technical shortcomings through an interactive theoretical-experimental program that distinguishes itself in no fewer than three ways: (i) construction of analytical and numerical frameworks to predict turbulence noise generation by graded poroelastic structures, from first principles; (ii) experimental validation of acoustic scaling laws for poroelastic edges, without background flow noise; and (iii) development of a glider to measure wing noise on the fly in a manner consistent with how owls hear their self-noise. The modeling and validation efforts aim to transform a biologically-inspired noise solution into a rational paradigm for passive aerodynamic noise control in low-speed flows and to create an experimental platform for future bionic owl noise-reduction studies. This project will also include K-12 educational outreach with the DaVinci Science Center (Allentown, PA), as well as integrate undergraduate research involvement through the Lehigh Biosystems Dynamics Summer Institute (in partnership with Northampton Community College) and through a design-build-fly competition between Lehigh and Penn State.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.