CAREER: Coupled Roughness/Pressure-Gradient Effects and Reducing the Complexity of Highly-Irregular Roughness in Wall Turbulence

职业：耦合粗糙度/压力梯度效应并降低壁湍流中高度不规则粗糙度的复杂性

• 批准号: 0644640
• 负责人: Kenneth Christensen
• 金额: $ 40万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-15 至 2013-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0644640&HistoricalAwards=false
• 关键词: CAREER; Coupled; Roughness; Pressure; Gradient

AbstractCBET-0644640K. Christensen, University of Illinois Urbana-ChampaignIntellectual merit: Canonical smooth-wall turbulence has been studied for many years and a relatively clear picture of its underlying structure now exists. However, the direct applicability of these efforts to technologically relevant flows, which often occur in complex geometries and in the presence of multiple noncanonical influences, like strong pressure gradients and highly-irregular surface roughness, is still unknown. The PI plans to expand his AFOSR research in the area of highly-irregular surface roughness by tackling two crucial topics central to advancing the science of modeling, predicting and controlling technologically-relevant turbulent flows in the presence of noncanonical influences. The majority of this effort will involve the study of turbulent boundary layers under the coupled influence of roughness replicated from turbine blades damaged by deposition and favorable-pressure-gradient (FPG) conditions. The PI has already made detailed PIV measurements under zero-pressure-gradient (ZPG) conditions at momentum thickness Reynolds numbers of 3900 and 11000. The PI plans to make similar measurements over smooth and rough walls with FPG conditions. This planned effort will address whether synergy between the two influences is similar in the transitionally- and fully-rough regimes and if wall similarity is valid under FPG conditions.A second research area will involve the design of topological models for highly-irregular surface roughness, specifically replicated from damaged turbine blades, using proper orthogonal decomposition (POD) with only the most energetic topological scales. Short fetches of the model topologies will be replicated and tested in turbulent channel flow using PIV to assess their ability to reproduce the flow features observed over the actual surface. Understanding issues such as the importance of the largest roughness scales compared to the finer scales of the surface topology will provide "guidelines" for the design of more representative simulated roughness topologies and would also assist in relating past simulated roughness studies to flows over practical roughness. Broader Impacts: The results of the proposed effort will have a direct impact on improved modeling and control of practical engineering flows, many of which have considerable influence on society (increased fuel efficiency of transportation systems for reduced oil consumption, for example). The students who will perform the bulk of this research will be actively recruited from under-represented groups using established programs at the University of Illinois (SURGE, MERGE, etc.) and will receive an exceptionally strong education in the areas of turbulence and advanced diagnostics. The educational component of this CAREER award includes the development of a graduate-level microscale fluid mechanics course and the revision of a graduate-level experimental methods of fluid mechanics course to include microscale measurement methods. The PI also plans to establish a student seminar series in fluid and thermal science to foster the growth of and collaboration amongst graduate students in the College of Engineering with similar research interests.

AbstractCBET-0644640K。克里斯滕森（Christensen），伊利诺伊大学Urbana-champaignIntellectual的功绩：经过多年的规范平滑墙的湍流已经进行了研究，现在已经存在相对清晰的其基础结构的情况。 但是，这些努力在技术相关的流中的直接适用性通常在复杂的几何形状中发生，并且在存在多种非规范影响的情况下，例如强压梯度和高度刻板的表面粗糙度，仍然未知。 PI计划通过解决在存在非范式影响的情况下推进建模，预测和控制技术与技术相关的湍流的核心核心，以扩大高度表面粗糙度领域的AFOSR研究。 这项工作的大部分将涉及研究湍流边界层，这些湍流边界层在被沉积和有利的压力梯度（FPG）条件受损的涡轮叶片复制的粗糙度的耦合影响下进行研究。 PI已经在零压力梯度（ZPG）条件下进行了详细的PIV测量，该条件在厚度雷诺数为3900和11000的情况下进行。PI计划在具有FPG条件下对光滑和粗糙的壁进行类似的测量。 这项计划的努力将解决两种影响之间的协同作用在过渡性和全面横向的制度中是否相似，以及在FPG条件下墙面相似性是否有效。第二个研究领域将涉及设计拓扑模型，以设计高度刻板的表面粗糙度，特别是由损坏的涡轮叶片（使用正式正交分解（POD））与最多的量表相吻合。 模型拓扑的简短获取将在湍流通道流中进行复制和测试，以评估其在实际表面上观察到的流量特征的能力。 了解诸如最大粗糙度量表的重要性与表面拓扑的尺度相比，最大的粗糙度量表的重要性将为设计更具代表性的模拟粗糙度拓扑的设计提供“指南”，并且还将有助于将过去的模拟粗糙度研究与实际上的粗糙度相关联。 更广泛的影响：拟议的努力结果将直接影响改善实践工程流的建模和控制，其中许多对社会的影响很大（例如，运输系统的燃油效率提高，以减少石油消耗）。 将使用伊利诺伊大学（Surge，Merge等）既定计划的代表性群体进行积极招募大部分研究的学生，并将在湍流和高级诊断领域接受高等教育。该职业奖的教育组成部分包括开发研究生水平的流体力学课程，并修订了流体力学课程的研究生级实验方法，以包括微观测量方法。 PI还计划建立一个在流体和热科学领域的学生研讨会系列，以促进具有类似研究兴趣的工程学院研究生的成长和合作。