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

Sreenivasan DMS9729251 “湍流：21世纪世纪的挑战”国际会议 狂风和咆哮的大火，龙卷风和飓风， 船舶和飞机，流经管道，泵，水泵， 以及动脉，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 影响到环境污染、天气、 预测，商业化学过程，飞机和船舶设计， 海洋动力学和天体物理学因此，湍流是 非常重要，需要认真对待。然而，这是一个 尽管经过了大约一百年的认真研究，但人们对这些学科知之甚少 research. 为什么会这样呢？这是陈词滥调，但真正的说，这是一个非常 困难的主题。困难来自于 湍流的复杂动力学特性，包括 例如，强非线性，同时存在一个大的 许多相互作用的自由度在一个广泛的范围内， 空间尺度，显著偏离统计平衡，等等 向前。可以激发超过10 ^{18}$$的自由度， 大气现象中典型的湍流。这使得充分 计算机模拟这种流动是不切实际的。实验研究 也因为泰勒的近似而遭受损失 假设和使用一维替代品 三维量。 在过去十年中，出现了一系列重要进展： 新的实验工具已经出现，并使直接测量成为可能 的时空场的湍流，和新的参数范围是 在实验中通过利用高压空气进行探索， 非常规流体如氦。直接数值模拟 成为研究湍流的有力工具。最近 计算机内存和速度的改进，特别是 集成的大规模并行机器的可用性， 使计算机模拟成为实验室的有益补充 实验此外，更深入地了解 非线性偏微分方程的快速获得。 总之，这些进展对 湍流动力学的理解，以及 工程实践中的工作模型。特别的进展是， 在被动混合物（例如染料，水蒸气， 污染物被湍流混合，但不反馈到 湍流运动本身）。例如，理论预测 在一类被动混合物的异常缩放。 这些预测反过来又得到了直接数值的支持。 仿真 评估这些最新进展，并在可能的情况下确定新的 为了指导该领域的工作，正在洛杉矶组织一次会议， 从1998年5月25日到28日在阿拉莫斯。这次会议是 由美国国家科学基金会和洛斯阿拉莫斯国家实验室资助， 国家实验室。会议的具体目标是 为全世界的科学家提供一个交流的机会， 基础研究和工程学的最新重要进展 应用流体湍流，并促进进一步发展 非线性科学这一广阔领域的最新进展。

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.