CAREER: Effects of thermal nonequilibrium on the acoustic noise radiated by a compressible turbulent boundary layer

职业：热非平衡对可压缩湍流边界层辐射的声学噪声的影响

基本信息

批准号：
1751965
负责人：
Stuart Laurence
金额：
$ 52.84万
依托单位：
University of Maryland, College Park
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-04-01 至 2023-03-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1751965&HistoricalAwards=false
关键词：
CAREER Effects thermal nonequilibrium acoustic

项目摘要

In gaseous flows over solid surfaces, the thin near-wall region can become chaotic and turbulent; these turbulent motions can then cause the generation of intense, outward-propagating sound waves, especially when the flow is supersonic. This project seeks to understand such noise generation when the gas in question (e.g., carbon dioxide, or high-temperature air) absorbs sound waves at certain frequencies. In particular, it is thought that by introducing such a gas into a near-surface flow of air, the noise generation can be reduced in configurations such as high-speed wind tunnels, where this noise can severely contaminate measurements. In conjunction, a variety of educational activities will be undertaken to introduce students at all levels to high-speed flows, including the creation of a YouTube channel where students can suggest objects to be flown in a Mach-8 wind tunnel.A systematic experimental study will be conducted to investigate turbulence-generated noise in the presence of a vibrationally relaxing gas. Acoustic attenuation measurements will be performed in quiescent pure gases (e.g., CO2, N2O) and gas mixtures to identify strong acoustically absorbing combinations at pressures and temperatures relevant to high-speed flows; results will be compared with theoretical attenuation models. Experiments in supersonic and hypersonic wind tunnels will examine the acoustic noise generated by a high-speed turbulent boundary layer: first, with the species identified in the earlier quiescent experiments as test gases; and subsequently with these species introduced locally into the boundary layer of an air flow. Effects of nonequilibrium on surface-pressure and turbulent velocity fluctuations will also be determined. This work will ultimately provide a fundamental understanding of thermal nonequilibrium effects on high-speed turbulence, as well as potentially provide a control mechanism for the reduction of acoustic noise in hypersonic 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.

在固体表面上的气态流动中，薄壁薄壁可以变得混乱和湍流。然后，这些湍流运动可能会导致强烈，外向传播的声波产生，尤其是当流量是超音速时。当相关气体（例如二氧化碳或高温空气）在某些频率下吸收声波时，该项目试图了解这种噪声的产生。特别是，人们认为，通过将这种气体引入近地表的空气流中，可以在诸如高速风隧道等配置中降低噪声，在这种配置中，这种噪声可以严重污染的测量。同时，将开展各种教育活动，以将各级的学生介绍到高速流动，包括创建YouTube频道，学生可以在Mach-8风隧道中提出对象进行的对象。一项系统的实验性研究将在存在振动放松气体的情况下进行研究以研究湍流产生的噪声。声学衰减测量将以静止的纯气体（例如CO2，N2O）和气体混合物进行，以鉴定与高速流相关的压力和温度下的强吸声吸收组合；结果将与理论衰减模型进行比较。超音速和超音速风隧道中的实验将检查由高速湍流边界层产生的声噪声：首先，在较早的静态实验中鉴定出物种是测试气体；随后，这些物种本地引入了空气流的边界层。还将确定非平衡对表面压力和湍流速度波动的影响。这项工作最终将提供对热无序影响对高速湍流的基本理解，并有可能为降低Hypersonic Wind Tunnels中声学噪声的控制机制提供了控制机制。此奖项反映了NSF的法定任务，并被认为是值得的支持。通过使用基金会的智力优点和更广泛影响的评论标准进行评估。