Fiber-Optic Hot-Wire/Hot-Film Anemometers for Turbulence Measurement

湍流的研究和控制对于开发具有最大性能和效率的下一代喷气发动机，燃烧室和发电厂至关重要，这些发动机预计将在日益恶劣的环境中运行，包括高温，高腐蚀性和大电磁干扰。热线/热膜风速仪可以准确地捕获和表征流动参数，对于湍流的基本理解至关重要。传统的热线风速计在这些环境下通常无法生存或性能显著降低。光纤热线/热膜风速仪是一种新兴技术，由于其介电结构和光学操作，具有在这些环境中执行的潜力。然而，目前的光纤热线/热膜风速计不能满足湍流研究所需的速度、灵敏度和空间分辨率。本申请中提出的研究旨在大幅提高光纤热线/热膜风速计的性能，使其成为恶劣环境中湍流测量的可行解决方案。该项目还将为光学领域的研究生和本科生提供研究和教育机会。K-12学校的学生和教师将通过几个现有的外展计划参与该项目。 该项目将研究超薄硅线和硅膜上的新加热和温度传感机制，以及可以大幅提高设备速度，灵敏度和空间分辨率的新型传感器解调方法。本计画包含五个研究目标：1）研究新的机制，以减少“端部传导”效应，改善风速计对高频流动分量的反应。2)开发新的无环氧树脂制造方法，用于恶劣环境下的传感器操作。3)研究提高光学谐振器品质因数的新机制，以改善风速计性能。4)通过新的恒温工作模式进一步提高传感器速度，该模式可自动补偿传感元件的热惯性。5)在室温和高温环境下表征和测试光纤风速计。拟议的研究将推进湍流研究领域，使热线/热膜风速计在恶劣环境中的新应用。小型化的光纤热线/薄膜还可用于表征偏远和/或难以进入的地点的液体/气体流动，并可应用于更广泛的社区，如生物学、医疗保健、化学工程和海洋学。该奖项反映了NSF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。

Non Technical Description:The study and control of turbulence are critical for the development of next generation jet engines, combustion chambers, and power plants with maximum performance and efficiency, which are expected to operate in increasingly harsh environment involving high temperature, high corrosivity, and large electromagnetic interference. Hot-wire/hot-film anemometry that can accurately capture and characterize the flow parameters is crucial for the fundamental understanding of turbulence. Traditional hot-wire anemometers often cannot survive or have significantly reduced performance under these environments. Fiber-optic hot-wire/hot-film anemometry is an emerging technology that has the potential to perform in these environments because of their dielectric structure and optical operation. Current fiber-optic hot-wire/hot-film anemometers, however, cannot meet the speed, sensitivity, and spatial resolution required for the study of turbulent flow. The research proposed in this application is aimed at drastically improving the performance of fiber-optic hot-wire/hot-film anemometers and make them a viable solution for turbulence measurement in harsh environment. The project will also provide research and education opportunities to graduate and undergraduate students in the field of optics. K-12 school students and teachers will be involved in the project through several existing outreach programs. Technical Description:The project will investigate new heating and temperature sensing mechanisms on ultra-thin silica wires and silicon films as well as novel sensor demodulation methods that can drastically improve the speed, sensitivity, and spatial resolution of the device. The project consists of five research objectives: 1) Investigate new mechanism to minimize the "end-conduction" effect for improved anemometer response to high-frequency flow components. 2) Develop novel epoxy-free fabrication methods for sensor operation under harsh environment. 3) Study novel mechanisms to increase the quality factor of the optical resonators for improved anemometer performance. 4) Further increase the sensor speed through a new constant-temperature operation mode that can automatically compensate for the thermal inertia of the sensing element. 5) Characterize and test the fiber-optic anemometers in room-temperature and high-temperature environments. The proposed research will advance the field of turbulence study by enabling the new applications of hot-wire/hot-film anemometry in harsh environments. Miniaturized fiber-optic hot-wires/films also allow to characterize liquid/gas flows in remote and/or difficult-to-access sites with applications in much broader communities such as biology, health care, chemical engineering, and oceanography.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.