An International Conference on Turbulence: Challenges for the 21st Century

湍流国际会议：21 世纪的挑战

• 批准号: 9729251
• 负责人: Katepalli Sreenivasan
• 金额: $ 1.4万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-04-15 至 1998-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9729251&HistoricalAwards=false
• 关键词: International; Conference; Turbulence; Challenges; 21st

Sreenivasan DMS9729251 "Turbulence: Challenges for the 21st Century" An International Conference Wind gusts and roaring fires, tornadoes and hurricanes, flows around ships and aircraft, flow through pipelines, pumps, turbomachinery, as well as arteries, are some examples of turbulent motion of fluids. Our ability to describe and predict turbulent phenomena strongly impacts such diverse fields as environmental pollution, weather prediction, commercial chemical processes, aircraft and ship design, ocean dynamics, and astrophysics. Turbulence is thus a subject of great importance and demands serious attention. Yet, it is one of the poorly understood subjects, despite about hundred years of serious research. Why is this so? It is trite but true to say that it is a very difficult subject. The difficulties stem from the fundamentally complex dynamical characteristics of turbulence including, for example, strong nonlinearity, the simultaneous presence of a large number of interacting degrees of freedom across a wide range of spatial scales, marked departure from statistical equilibrium, and so forth. More than $10^{18}$ degrees of freedom can be excited in turbulent flows typical of atmospheric phenomena. This makes full computer simulation of such flows impractical. Experimental studies have also suffered because of approximations such as Taylor's hypothesis and the use of one-dimensional surrogates for three-dimensional quantities. A confluence of important advances has occurred in the last decade: new experimental tools have emerged, and enabled direct measurement of spatio-temporal fields of turbulence, and new parameter ranges are being explored in experiments by harnessing air at high pressures or unconventional fluids such as helium. Direct numerical simulation has become a powerful tool for the study of turbulence. Recent improvements in computer memory and speed, especially the availability of we ll-integrated massively parallel machines, have made computer simulation a useful complement to laboratory experiments. In addition, greater insights into the behavior of nonlinear partial differential equations are being acquired rapidly. Together, these advances have had a qualitative impact on the understanding of turbulence dynamics, and on the development of working models in engineering practice. Particular progress has been achieved in the case of passive admixtures (such as dye, water vapor, pollutants which are mixed by turbulence, but do not feed back to the turbulent motion itself). For example, theoretical predictions have been made for anomalous scaling in a class of passive admixtures. These predictions are in turn supported by direct numerical simulation. To assess these recent advances and define, where possible, new directions for the field, a conference is being organized at Los Alamos between the 25th and 28th of May 1998. The conference is being supported by the National Science Foundation and the Los Alamos National Laboratory. The specific goal of the conference is to provide an opportunity for scientists world-wide to communicate recent critical advances in fundamental studies and engineering applications of fluid turbulence, and to foster further development of this broad field of nonlinear science.

Sreenivesan DMS9729251“湍流：21世纪的挑战”国际会议上，阵风和咆哮的大火、龙卷风和飓风、围绕船舶和飞机的流动、通过管道、泵、透平机械以及动脉的流动，都是流体湍流运动的一些例子。我们描述和预测湍流现象的能力强烈影响着环境污染、天气预报、商业化学过程、飞机和船舶设计、海洋动力学和天体物理等多个领域。因此，湍流是一个非常重要的问题，需要认真关注。然而，尽管经过了近百年的认真研究，但它仍然是一个鲜为人知的主题。为什么会这样呢？老生常谈，但可以说，这是一个非常困难的主题。这些困难源于湍流的基本复杂的动力学特征，包括，例如，强烈的非线性，在广泛的空间尺度上同时存在大量相互作用的自由度，显著偏离统计平衡，等等。在典型的大气现象的湍流中，可以激发超过10个自由度。这使得对这种流动进行全面的计算机模拟是不切实际的。实验研究也因泰勒假说和使用一维替代物代替三维量等近似而受到影响。在过去的十年里，出现了一系列重要的进展：出现了新的实验工具，使人们能够直接测量湍流的时空场，并通过利用高压空气或氦等非传统流体在实验中探索新的参数范围。直接数值模拟已成为研究湍流的有力工具。最近在计算机内存和速度方面的改进，特别是大规模并行机的出现，使计算机模拟成为实验室实验的有益补充。此外，人们正在迅速获得对非线性偏微分方程组行为的更深入的了解。总而言之，这些进展对湍流动力学的理解和工程实践中工作模型的发展产生了定性的影响。在被动混合物(如染料、水蒸气、污染物等)方面取得了特别的进展，这些污染物被湍流混合，但不会反馈到湍流运动本身。例如，对一类被动混合物中的反常标度进行了理论预测。这些预测反过来又得到了直接数值模拟的支持。为了评估这些最新进展并在可能的情况下确定实地的新方向，1998年5月25日至28日在洛斯阿拉莫斯组织了一次会议。这次会议得到了美国国家科学基金会和洛斯阿拉莫斯国家实验室的支持。会议的具体目标是为世界各地的科学家提供一个机会，交流流体湍流基础研究和工程应用方面的最新关键进展，并促进这一广泛的非线性科学领域的进一步发展。