Fundamentals of Wall-Bounded Turbulence at Extreme Reynolds Numbers

了解高雷诺数壁面湍流具有重要的基础和实际意义，因为它在各种流动中都能观察到，包括飞机和轮船上的流动，管道和管道中的流动，以及地球大气中的流动。然而，大多数实验室和计算研究局限于相对较低的雷诺数，因此湍流中最基本的问题之一是如何将在低雷诺数下获得的知识推广到高雷诺数。此外，我们现在知道，不同的流动可以表现出不同的行为：管道、通道和边界层可以表现出显著不同的行为，那么我们如何协调这些不同的观测结果呢？在这里，我们建议对管流和边界层中非常高的雷诺数的湍流进行全面的研究，以帮助回答这些问题。我们处于进行这项工作的独特位置，因为我们拥有流动设备，可以在管道和边界层中产生非常高的雷诺数湍流，并且我们还开发了(在之前NSF的支持下)能够测量湍流的新探头，其空间和时间分辨率比传统的热线仪器小约两个数量级。这些工具使我们能够研究雷诺数至少比以前的实验室研究在完全空间和时间分辨率条件下能够达到的高一个数量级。拟议工作的智力价值取决于我们试图回答的基本问题。具体地说，我们将使用我们的测量来回答最近发现的关于高雷诺数下湍流行为的具体争议。例如，在湍流边界层中的观测表明，远离壁面的大尺度湍流对靠近壁面的湍流有很强的影响。在湍流管流中的观测没有显示出这种相关性。了解这种差异是开发近壁模型的关键一步，这些模型对于准确预测工业和其他实际应用中的湍流是必不可少的。因此，这项工作的更广泛影响主要是提高我们预测和管理高雷诺湍流数流动的能力。通过这种方式，我们希望支持更安全、更高效的飞机和船舶的设计，并提供更好的模型，以提高全球循环模型的质量和精度，此外还帮助设计更好的石油和天然气管道系统。此外，我们将建立一个积极的计划，利用这项研究工作，帮助从K-12到博士后水平的科学和工程专业的学生，并根据我们的研究经验，通过期刊出版物、会议报告和教育材料尽可能广泛地传播新知识。

1064257SmitsThe understanding of high Reynolds number wall-bounded turbulence is of great fundamental and practical importance, since it is observed in a wide range of flows, including flows over aircraft and ships, flow in pipelines and ducts, and the flow in the Earth's atmosphere. However, most laboratory and computational studies are restricted to relatively low Reynolds numbers, and so one of the most fundamental questions in turbulence is how knowledge gained at low Reynolds number can be extended to high Reynolds numbers. In addition, we now know that different flows can behave differently: pipes, channels, and boundary layers can display significantly different behavior, and so how do we reconcile these different observations?Here, we propose a comprehensive study of turbulence at very high Reynolds numbers in pipe flows and boundary layers, to help answer these questions. We are uniquely positioned to conduct this work because we have flow facilities that can produce very high Reynolds number turbulent flows in pipes and boundary layers, and we have also developed (under previous NSF support) a new probe capable of measuring turbulence with a spatial and temporal resolution about two orders of magnitude smaller than conventional hot wire instrumentation. These tools allows us to study Reynolds numbers are at least an order of magnitude higher than previous laboratory studies were able to achieve under conditions of full spatial and temporal resolution.The intellectual merit of the proposed work rests on the fundamental questions we seek to answer. Specifically, we will use our measurements to answer specific controversies recently discovered regarding the behavior of turbulence at high Reynolds number. For example, observations in turbulent boundary layers show a strong influence of the large-scale turbulence away from the wall on the turbulence near the wall. Observations in turbulent pipe flow do not show this correlation. Understanding the difference is a crucial step in developing near-wall models that are essential for accurate predictions of turbulent flow in industry and other practical applications. Hence the broader impact of the work is primarily to improve our ability to predict and manage high Reynolds turbulent number flows. In this way, we hope to support the design of safer and more efficient aircraft and ships, and provide better models to improve the quality and accuracy of, for example, Global Circulation Models, in addition to helping to design better oil and gas pipeline systems. Furthermore, we will build an aggressive program to use this research work to help educate students in science and engineering, from K-12 to postdoctoral levels, and to distribute the new knowledge as widely as possible through journal publications, conference presentations, and educational materials based on our research experience.