权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Development of New Ultrasonic Measurement System for Turbulence and Elucidation of the Limit of Transport in Turbulence

新型湍流超声波测量系统的开发及湍流传输极限的阐明

基本信息

批准号：
16206020
负责人：
SANO Masaki
金额：
$ 31.53万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2007
项目状态：
已结题

项目摘要

Study on turbulence is important for every area of science and technology. Among them thermal turbulence has been popular research subjects, since the prediction of heat transport, diffusion and mixing in thermal turbulence is indispensable fur both fundamental and application researches. In this research project we aimed to develop a new ultrasonic measurement method far thermal turbulence and explore stricture in turbulence to elucidate the scaling law of beat transport due to turbulence. We used mercury as a test liquid. Because, the fact that its kinematic viscosity is low and kinetic boundary layer is thinner than the thermal boundary layer enables us to explore high Rayleigh, high Reynolds number in laboratory Although ultrasonic velocimeter (USV) is known for long time for flow rate measurements, it has never been applied to measurement of turbulence due to limitation in temporal resolution and accessible maximum velocity We succeeded to use USV for thermal turbulence, because t … More he maximum velocity and the highest frequency in thermal turbulence is relatively low even at high Rayleigh number compared with other turbulence, such as grid turbulence and wake turbulence. We developed 3 measurement systems far thermal turbulence 1. Three ultrasonic transducers monitoring along X, Y, and Z axes simultaneously. 2. One moving transducer without destructing the wall of the convection cell. 3. Multi-thermosensors (32 thermistors) embedded in the cell bottom and the side wall which enable us to monitor the structure of the mean flow in thermal turbulence. By using these measurement systems, we successfully measured the energy spectrum directly from instantaneous measurement of the velocity filed without utilizing Taylor hypothesis, and found that Bolgiano-Obkhov scaling law holds in thermal turbulence. We further elucidated structure of the mean flow existing in thermal turbulence. Their structures, dynamics, and stabilities strongly depend on the aspect ratio of the convection cell. Less

湍流研究对于科学技术的各个领域都很重要。其中热湍流一直是热门研究课题，热湍流中热传输、扩散和混合的预测无论是基础研究还是应用研究都不可或缺。在本研究项目中，我们旨在开发一种新的远热湍流超声测量方法，并探索湍流的狭窄性，以阐明湍流引起的拍速传输的标度规律。我们使用汞作为测试液体。因为，它的运动粘度低，运动边界层比热边界层薄，使我们能够在实验室中探索高瑞利、高雷诺数。虽然超声波测速仪（USV）在流量测量方面早已为人所知，但由于时间分辨率和可达到的最大速度的限制，它从未应用于湍流的测量。我们成功地将USV用于热测量湍流，因为与其他湍流（例如网格湍流和尾流湍流）相比，即使在高瑞利数下，热湍流的最大速度和最高频率也相对较低。我们开发了 3 种远热湍流测量系统 1. 三个超声波传感器沿 X、Y 和 Z 轴同时监测。 2. 一个可移动的换能器，不会破坏对流室的壁。 3. 多个热敏传感器（32个热敏电阻）嵌入单元底部和侧壁，使我们能够监测热湍流中的平均流动的结构。通过使用这些测量系统，我们成功地直接从速度场的瞬时测量中测量了能谱，而无需利用泰勒假设，并发现Bolgiano-Obkhov标度定律在热湍流中成立。我们进一步阐明了热湍流中存在的平均流的结构。它们的结构、动力学和稳定性很大程度上取决于对流室的纵横比。较少的