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.

摘要CBET-0644640K。克里斯滕森，伊利诺伊大学厄巴纳-香槟分校智力优势：规范光滑壁湍流已经被研究了很多年，现在已经对其基础结构有了相对清晰的了解。 然而，这些努力对技术相关流动的直接适用性仍然未知，这些流动通常发生在复杂的几何形状和存在多种非规范影响的情况下，例如强压力梯度和高度不规则的表面粗糙度。 该 PI 计划通过解决两个关键主题，扩大其在高度不规则表面粗糙度领域的 AFOSR 研究，这两个主题对于推进建模科学、预测和控制存在非规范影响的技术相关的湍流至关重要。 这项工作的大部分内容将涉及在由沉积和有利压力梯度（FPG）条件损坏的涡轮叶片复制的粗糙度的耦合影响下研究湍流边界层。 PI 已经在动量厚度雷诺数为 3900 和 11000 的零压力梯度 (ZPG) 条件下进行了详细的 PIV 测量。PI 计划在 FPG 条件下对光滑和粗糙的墙壁进行类似的测量。 这项计划的工作将解决两种影响之间的协同作用在过渡粗糙状态和完全粗糙状态中是否相似，以及壁相似性在 FPG 条件下是否有效。第二个研究领域将涉及高度不规则表面粗糙度的拓扑模型设计，专门从受损的涡轮叶片复制而来，仅使用具有最高能量拓扑尺度的适当正交分解（POD）。 将使用 PIV 在湍流通道流中复制和测试模型拓扑的短获取，以评估其再现在实际表面上观察到的流动特征的能力。 了解最大粗糙度尺度与表面拓扑的更精细尺度相比的重要性等问题将为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粗糙度上的流动联系起来。 更广泛的影响：拟议工作的结果将对改进实际工程流程的建模和控制产生直接影响，其中许多对社会具有相当大的影响（例如，提高运输系统的燃油效率以减少石油消耗）。 执行大部分研究的学生将使用伊利诺伊大学的既定项目（SURGE、MERGE 等）从代表性不足的群体中积极招募，并将在湍流和高级诊断领域接受非常强大的教育。该职业奖的教育部分包括开发研究生水平的微尺度流体力学课程，以及修订研究生水平的流体力学课程实验方法以包括微尺度测量方法。 PI 还计划建立流体和热科学领域的学生研讨会系列，以促进工程学院具有类似研究兴趣的研究生的成长和合作。