The small-scale structure of the fluctuating passive scalar field in a turbulent boundary layer

摘要提案编号： CTS-0303406提案类型： 主要负责人：唐纳德·R。网站机构： 格鲁吉亚理工学院湍流边界层中脉动被动标量场的小尺度结构湍流中被动标量的混合和输运是许多自然和工程环境中发生的重要过程。 常见的例子包括水体中的污染物排放、大气中的化学羽流以及反应堆中的化学混合。 尽管数十年的研究旨在了解湍流传输的动力学，标量场继续挑战准确的理论预测。 缺乏一个通用的理论来预测湍流传输的统计性质，最终需要实验测试来预测和优化混合效率的许多实际情况。 这个过程是低效和昂贵的，因此一个普遍的理论湍流波动的标量仍然是非常可取的。 本文研究湍流剪切流有以下目的：（1）检验标量方差耗散率的动力学特性;（2）研究多点离散器作为表征小尺度湍流结构的工具的性能和实用性，以及它与传统结构函数的关系。 此外，我们建议检查各向同性和各向异性组件的结构函数和它们各自的标度行为。 实验将进行化学羽流在湍流边界层的明渠流动。 平面激光诱导荧光（PLIF）技术将用于记录高施密特数浓度场的时间序列。 测量解决了标量场的巴彻勒长度尺度。 将研究三种雷诺数和三种平均标量梯度情况之间的变化。 提出的实验结果将影响建模策略和我们的基本理解之间的耦合小尺度和大尺度的行为在湍流剪切流。 一名研究生（博士）一名本科生将接受先进实验技术和湍流基础研究方面的培训。 格鲁吉亚理工学院是代表性不足群体研究生教育的全国领导者，将尽一切努力吸引这样的学生参加这个项目。

ABSTRACTPROPOSAL NO.: CTS-0303406PROPOSAL TYPE: INVESTIGATOR INITIATEDPRINCIPAL INVESTIGATORS: DONALD R. WEBSTERINSTITUTION: GEORGIA TECH. THE SMALL-SCALE STRUCTURE OF FLUCTUATING PASSIVE SCALAR FIELD IN A TURBULENT BOUNDARY LAYERMixing and transport of passive scalars in turbulent flows are important processes occurring in many natural and engineered environments. Common examples include contaminant discharges in water bodies, chemical plumes in the atmosphere, and chemical mixing in reactors. Despite decades of research aimed at understanding the dynamics of turbulent transport, scalar fields continue to defy accurate theoretical predictions. The lack of a general theory to predict the statistical nature of turbulent transport ultimately requires experimental tests to predict and optimize mixing efficiency for many practical situations. This procedure is inefficient and costly, thus a universal theory for turbulent fluctuations of scalar quantities continues to be highly desirable. This study of a turbulent shear flow has the following objectives: (1) examine the dynamics of the scalar variance dissipation rate, and (2) study the behavior and usefulness of multi-point correlators as a tool to represent small-scale turbulence structure and its relation to the traditional structure functions. We additionally propose to examine the isotropic and anisotropic components of structure functions and their respective scaling behavior. Experiments will be performed for a chemical plume in a turbulent boundary layer of an open channel flow. The planar laser induced fluorescence (PLIF) technique will be used to record time series of the high Schmidt number concentration fields. The measurements resolve the Batchelor length scale of the scalar field. Variation among three Reynolds numbers and three mean scalar gradient cases will be examined. The proposed experimental results will impact both modeling strategies and our fundamental understanding of the coupling between small-scale and large-scale behavior in turbulent shear flows. One graduate student (Ph.D. level) and one undergraduate student will be trained in advanced experimental techniques and fundamental turbulence research. Georgia Tech is a national leader in graduate education of underrepresented groups, and every effort will be made to attract such a student to this project..