EAGER: Improving the Aeroacoustic Properties of Hybrid Anechoic Wind Tunnels

风洞是工程和科学过程的基本组成部分，用于开发更安静、更高效的飞机、风力涡轮机和其他系统。混合消声风洞是大约13年前推出的，它提供了一种大大提高与流动产生的噪声有关的风洞试验的准确性和范围的方法。这种配置已经被世界各地的许多研究机构采用，它依赖于“声学窗”——一种对声音透明但基本上不透水的大型拉伸织物面板。这种窗户是由市售的凯夫拉纤维织物制成的，它具有许多理想的特性，但这种织物是为复合材料制造而设计的。专为风洞应用而设计的凯夫拉纤维织物保证了额外的好处——更安静的测试环境和可以监控流量的嵌入式仪器。在这个项目下，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个短期研究计划来开发这些材料。这项创新的、潜在的高回报的努力有望将混合消声测试的优势带到全国范围内的设施，并极大地促进了更安静、更高效的车辆和系统的开发。该项目还将致力于博士后、研究生和本科生的研究教育。这项研究是基于对凯夫拉纤维作为隔音窗产生高频噪音（10kHz）的观察，这可能会限制该技术在国家规模风洞设施中的应用，这些风洞设施为工业和政府的车辆开发进行应用模型规模测试。假设是，噪音是由织物上的毛孔产生的，这些毛孔没有有用的气动声学功能。调整织物以消除毛孔需要多学科合作，需要对气动声学应用的最佳织物设计进行系统研究。这项工作是由弗吉尼亚理工大学、佛罗里达大西洋大学和北卡罗来纳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机制造所需的改性织物，并研究嵌入传感器的可行性。风洞实验将在弗吉尼亚理工大学进行，旨在记录和理解织物的气动声学性能，这也将为传感器的选择和要求提供输入。理论建模和对声源性质的理解将在佛罗里达大西洋大学进行。总之，这项工作有望为当前和计划中的混合消声风洞提供最佳声学窗设计和嵌入式传感器的可靠建议。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。

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.