ary currents in turbulent flows over rough wallsSecond

湍流流过粗糙的墙壁第二

• 批准号: EP/V00199X/1
• 负责人: Bharathram Ganapathisubramani
• 金额: $ 98.65万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV00199X%2F1
• 关键词: ary; currents; turbulent; flows; over

A majority of engineering and environmental flows occur over surfaces that exhibit spatial variations in roughness and/or topography. When a turbulent wall-flow evolves over such surfaces, it may exhibit unusual physical properties, depending on the relationship between the dominant length-scales of the surface and that of the flow. Specifically, when the dominant length-scale(s) of the surface in the cross-stream direction become(s) comparable to the dominant length-scale of the flow (such as boundary layer thickness or water-depth), then the flow also exhibits large-scale spatial heterogeneity that is locked-on to the surface heterogeneity. This flow heterogeneity is expressed in the form of localised secondary currents (SCs) that often extend across the entire depth of the flow and manifest themselves as large 'time-averaged' streamwise vortices accompanied by low- and high-speed regions. This surface-induced flow heterogeneity invalidates some of the fundamental tenets of turbulent wall-flows that were developed for flows over homogeneous surfaces. Therefore, current predictive tools that rely on these tenets can neither accurately predict nor offer insights into the complex physics of flows that contain surface-induced SCs. The significant effects of surface-induced SCs have recently been recognised in at least two disparate areas: 1) Performance of engineering systems such as in-service turbine blades, bio-fouled ship hulls and flow control; and 2) Understanding of the river flow dynamics with applications in flood management, eco-hydraulics and sediment transport. Over recent years, Southampton, Aberdeen, Glasgow and UCL have invested considerable efforts in advancing both these areas. Given the burgeoning interest in this topic, it would be timely to harness the synergies between these four leading groups to develop comprehensive understanding of turbulent flows in the presence of surface-induced SCs and establish a novel transformative framework to predict such flows. This project will leverage the expertise, domain knowledge and infrastructure of four leading groups in the above-mentioned areas to bring about a paradigm shift in our approach to flows over heterogeneous surfaces that generate secondary currents. A comprehensive series of physical experiments (at Southampton & Aberdeen) and complementary numerical simulations (at Glasgow & UCL) will be performed to generate unprecedented data on surface-induced SCs. We will compare and contrast the behaviour of SCs across all four canonical wall-flows (boundary layers, open-channels, pipes and closed-channels) for the first time. The obtained data will underpin identification and validation of potential universalities (and differences) in drag mechanisms and momentum/energy transfer in these flows in the presence of surface-induced SCs. Synthesising the insights obtained from the data, a new framework leading to physics-informed semi-empirical and and theoretically-based numerical models will be developed to predict and optimise the influence of surface-induced SCs on turbulent wall-flows relevant to engineering/environmental applications.

大多数工程和环境流动发生在粗糙度和/或地形空间变化的表面上。当湍流壁流在这样的表面上演变时，它可能表现出不寻常的物理性质，这取决于表面的主要长度尺度与流动长度尺度之间的关系。具体而言，当横流方向表面的优势长度尺度(s)与流动的优势长度尺度（如边界层厚度或水深）相当时，则流动也表现出锁定在表面非均质性上的大尺度空间非均质性。这种流动的非均质性以局部次级流（SCs）的形式表现出来，这些次级流通常延伸到流动的整个深度，并表现为伴随着低速和高速区域的大型“时间平均”流向漩涡。这种表面诱导的流动非均质性使紊流壁面流动的一些基本原理失效，这些基本原理是为均匀表面上的流动而发展起来的。因此，目前依赖于这些原则的预测工具既不能准确预测也不能深入了解含有表面诱导SCs的流体的复杂物理特性。最近，至少在两个不同的领域已经认识到表面诱导SCs的显著影响：1)工程系统的性能，如在用涡轮叶片、生物污染船体和流动控制；2)了解河流流动动力学及其在洪水管理、生态水力学和输沙中的应用。近年来，南安普顿、阿伯丁、格拉斯哥和伦敦大学学院在这两个领域都投入了相当大的努力。鉴于人们对这一主题的兴趣日益浓厚，利用这四个领先小组之间的协同作用，全面了解表面诱导的纳米颗粒存在下的湍流，并建立一个新的变革框架来预测这种流动，将是及时的。该项目将利用上述领域的四个领先小组的专业知识、领域知识和基础设施，为我们在产生二次电流的异质表面上的流动方法带来范式转变。将进行一系列全面的物理实验（在南安普敦和阿伯丁）和互补的数值模拟（在格拉斯哥和伦敦大学学院），以生成有关表面诱导SCs的前所未有的数据。我们将首次比较和对比SCs在所有四种典型壁流（边界层、开放通道、管道和封闭通道）上的行为。获得的数据将支持识别和验证在表面诱导SCs存在的情况下这些流动中阻力机制和动量/能量转移的潜在普遍性（和差异性）。综合从数据中获得的见解，将开发一个新的框架，导致物理知情的半经验和基于理论的数值模型，以预测和优化表面诱导的SCs对与工程/环境应用相关的湍流壁流的影响。

项目成果

Scaling of secondary flows with surface parameters: A linear approach

使用表面参数缩放二次流：线性方法

• DOI: 10.1016/j.ijheatfluidflow.2023.109148
• 发表时间: 2023
• 期刊: International Journal of Heat and Fluid Flow
• 影响因子: 2.6
• 作者: Zampino G

Defining an equivalent homogeneous roughness length for turbulent boundary layers developing over patchy or heterogeneous surfaces

定义在斑片或异质表面上形成的湍流边界层的等效均匀粗糙度长度

• DOI: 10.1016/j.oceaneng.2022.113454
• 发表时间: 2023
• 期刊: Ocean Engineering
• 影响因子: 5
• 作者: Hutchins N

Linear predictions of secondary flows over modulated walls

调制壁上二次流的线性预测

• DOI: 10.52843/cassyni.k5yqtf
• 发表时间: 2023
• 作者: Lasagna D

Linearised Reynolds-averaged predictions of secondary currents in turbulent channels with topographic heterogeneity

具有地形异质性的湍流通道中二次电流的线性雷诺平均预测

• DOI: 10.1017/jfm.2022.478
• 发表时间: 2022
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Zampino G