Multiscale Interactions in Turbulent Flows: Experiments and Simulation

提案编号： CTS-0553314主要制造商：C. Meneveau研究所：约翰霍普金斯大学湍流多尺度相互作用：实验模拟这项研究将解决几个关键方面的理解和湍流与多尺度边界条件相互作用的数值模拟。具体而言，一个新的数据库的湍流通过分形海崖体和网格将产生使用热和粒子图像测速在风洞中。分形对象具有尺度差异大、复杂性强等特点，但其描述方法简单、标准化。因此，他们提供了一个优雅的理想化的实际相互作用之间的湍流和边界在实际应用中，边界的特点是由多个长度尺度。这些数据将包括表征湍流的流量测量值以及作用在分形物体上的阻力测量值。所提出的工作的一个显着的动机是需要验证和支持一个新的预测工具，称为重整化数值模拟（RNS）的进一步改进。该技术使用从大尺度动态确定的阻力系数对未解析特征建模。 RNS将被应用于模拟流过分形海崖体阵列和网格的流动，并将预测的力和流动特征与测量结果进行比较。另一个目标是使用空间滤波和适当的统计技术，使用数据来研究规模的相互作用。湍流研究和模拟是理解和预测具有多尺度复杂行为和多自由度的系统的更大推动力的一部分。今天，对这些系统的大规模数值模拟是科学讨论的中心，具有重要的社会和政治影响（全球变化，能源等）。此外，适当验证的RNS方法的发展适用于流与分形边界可能会产生更广泛的影响。分形已被用作许多学科的描述工具，如生物学（分支血液网络，肺结构，珊瑚），天体物理学（宇宙的大尺度结构，行星际磁场的不连续性），地球科学（分形海岸线，植被，云）。RNS将分形的几何思想扩展到动力学中。拟议工作的教育影响将集中在研究生教育和培训，强调物理实验和模拟之间的相互作用。教育推广将与工程学校教育推广中心（CEO）合作进行。在2006年和2007年的夏天，一名高中教师将被邀请从事一个项目，该项目涉及分形网格后面湍流尾流的流动可视化。

PROPOSAL NO.: CTS-0553314PRINCIPAL INVESTIGATOR: C. MENEVEAUINSTITUTION: JOHNS HOPKINS UNIVERSITY MULTISCALE INTERACTIONS IN TURBULENT FLOWS: EXPERIMENTS & SIMULATIONSThis research will address several critical aspects in understanding and numerical modeling of turbulent flows interacting with multiscale boundary conditions. Specifically, a new database of turbulent flow through fractal bluff bodies and grids will be generated using thermal and particle image velocimetry in a wind tunnel. Fractal objects display large scale-disparity and complexity while being amenable to simple and standardized description. Hence, they offer an elegant idealization of the actual interactions between turbulence and boundaries in practical applications where boundaries are characterized by multiple length-scales. The data will include flow measurements characterizing the turbulence as well as measurements of the drag forces acting on the fractal objects. A salient motivation for the proposed work is the need to validate and support further improvements of a new prediction tool, called Renormalized Numerical Simulation (RNS). This technique models forces on unresolved features using drag coefficients determined dynamically from the large scales. RNS will be applied to model flow across fractal bluff body arrays and grids, and predicted forces and flow features will be compared with the measurements. Another objective is to use the data to study scale interactions using spatial filtering and appropriate statistical techniques. Turbulence research and simulation are part of a larger push to understand and predict systems with multiscale complex behavior and many degrees of freedom. Large-scale numerical simulation of such systems is, today, at center stage of scientific discussions with important societal and political ramifications (global change, energy, etc.). Also, the development of properly validated RNS methodology applied to flows with fractal boundaries may yield broader impacts. Fractals have been used as a descriptive tool in many disciplines such as biology (branching blood network, pulmonary structures, corals), astrophysics (large-scale structure of the universe, intermittency of interplanetary magnetic fields), geosciences (fractal coastlines, vegetation, clouds). RNS extends the geometric idea of fractals to the dynamics. Educational impact of the proposed work will focus on graduate education and training that stresses the interplay between physical experimentation and simulation. Educational Outreach will take place in collaboration with the Engineering Schools Center for Educational Outreach (CEO). In the summer of 2006 and 2007, a high-school teacher will be invited to work on a project dealing with flow visualization of turbulent wakes behind fractal grids.