EAGER: Improving the Aeroacoustic Properties of Hybrid Anechoic Wind Tunnels

风洞是用于开发更安静、更高效的飞机、风力涡轮机和其他系统的工程和科学过程的基本部分。大约13年前引入的混合消声风洞提供了一种方法，大大提高了与流动产生的噪声有关的风洞测试的准确性和范围。这种结构已经被世界各地的许多研究机构采用，依赖于“声学窗”--对声音透明但基本上不透流的大片张紧的布料。这种窗户是由商业上可获得的芳纶织物制成的，这种织物具有许多用于此目的的理想特性，但该织物是为复合材料制造而设计的。专门为风洞应用而设计的芳纶织物承诺了额外的好处--更安静的测试环境和可以监控流量的嵌入式仪器。在该项目下，一个由纺织、声学和空气动力学研究人员组成的跨学科团队将进行一项短期研究计划，以开发这些材料。这一创新的、潜在的高回报努力，有望将混合消声测试的优势带到国家规模的设施中，并极大地促进更安静、更高效的车辆和系统的开发。该项目还将致力于博士后、研究生和本科生水平的研究教育。这项研究的基础是观察到，用作声窗的芳纶织物会在高频(10 KHz)产生噪声，这可能会限制这项技术在国家级风洞设施中的应用，这些风洞设施为行业和政府的车辆开发执行应用模型尺度测试。假设噪音是由织物上的气孔产生的，这些气孔没有起到有用的空气声学功能。调整织物组织以消除气孔需要多学科的协作，以便对气动声学应用的最佳织物设计进行系统研究。这项工作是由来自弗吉尼亚理工大学、佛罗里达大西洋大学和北卡罗来纳州州立大学的一组研究人员完成的。北卡罗来纳州立大学的研究小组将使用一台研究织布机，制造所需的改装面料，并调查嵌入传感器的可行性。弗吉尼亚理工大学将进行风洞实验，以记录和了解织物的气动声学性能，该实验室还将提供关于传感器选择和要求的信息。对声源性质的理论建模和理解将在佛罗里达大西洋大学进行。这一努力预计将为当前和计划中的混合消声风洞产生最佳声窗设计和嵌入式传感器的强有力的建议。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Wind tunnels are a fundamental part of the engineering and scientific process used to develop quieter and more efficient aircraft, wind turbines, and other systems. The hybrid anechoic wind tunnel, introduced some 13 years ago, provides a way to substantially increase the accuracy and scope of wind tunnel tests concerned with flow generated noise. This configuration, which has already been adopted by a number of research facilities across the world relies on “acoustic windows” – large panels of tensioned fabric that are transparent to sound but largely impervious to flow. Such windows have been made from commercially available Kevlar fabric which has many desirable characteristics for this purpose, but the fabric was designed for composites manufacture. A Kevlar fabric explicitly designed for wind tunnel applications promises additional benefits – an even quieter test environment and embedded instrumentation that can monitor the flow. Under this project, an interdisciplinary team of textiles, acoustics, and aerodynamics researchers will conduct a short-term research program to develop these materials. This innovative, potentially high payoff effort, promises to bring the advantages of hybrid anechoic testing to national scale facilities and greatly enhance the development quieter and more efficient vehicles and systems. This project will also be dedicated to research education at the postdoc, graduate and undergraduate levels. This research is based upon the observation that Kevlar fabric used as acoustic windows generates noise at high frequencies (10kHz) that potentially limits the application of this technology in the context of national scale wind tunnel facilities that perform applied model scale testing for vehicle development by industry and government. The hypothesis is that the noise is made by pores in the fabric that serve no useful aeroacoustic function. Adjusting the weave to eliminate the pores requires the multi-disciplinary collaboration needed to perform a systematic study of the optimum fabric design for aeroacoustic applications. The work is being performed by a team of researchers from Virginia Tech, Florida Atlantic University, and NC State. The NC State group will use a research loom fabricate the needed modified fabrics and also investigate the feasibility of embedding sensors. Wind tunnel experiments directed at documenting and understanding the aeroacoustic performance of the fabrics will be performed at Virginia Tech, which will also provide input on sensor choices and requirements. Theoretical modeling and understanding of the nature of the acoustic source will be performed at Florida Atlantic University. Together this effort is expected to generate robust recommendations for optimal acoustic window design and embedded sensors that can be adopted by current and planned hybrid anechoic wind tunnels.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.