EPSRC-CBET:Turbulent flows over heterogeneous multiscale surfaces

EPSRC-CBET：异质多尺度表面上的湍流

基本信息

批准号：
1738918
负责人：
Charles Meneveau
金额：
$ 35.89万
依托单位：
Johns Hopkins University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-07-01 至 2022-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1738918&HistoricalAwards=false
关键词：
EPSRC CBET Turbulent flows over

项目摘要

In almost all engineering and environmental flows, turbulent boundary layers (the part of the flow closest to a given surface) are in the rough-wall regime. Typical examples include boundary layers developing over surface irregularities on aircraft and wind turbine blades, macro bio-fouled ship hulls, edges of forests or wind-farms, urban canopies, crop boundaries, river-beds, and wind over rough seas. Despite decades of sustained research, accurate predictions of momentum transfers and/or skin-friction drag based on geometric information about the surface alone are difficult. This is primarily because in most cases, the topography of surface roughness is multi-scale, that is to say, it contains a wide variety of roughness length scales. Moreover, the variation in the range of roughness length scales and the distribution of the roughness features is heterogeneous across the surface. Current predictive approaches, designed mostly for homogeneous and single-scale roughness element distributions, can neither accurately predict nor offer insights into the complex physics of flow over multi-scale heterogeneous surfaces. In this collaborative research,a systematic approach to characterize drag and the mechanisms of momentum transfers in flows over heterogeneous multi-scale surfaces will be applied. This research will be broadly relevant to a large number of industries where flows over rough surfaces are critical for performance. In the transportation industry for example, the drag incurred by rough surfaces has important impact on transportation efficiency and its environmental footprint. This research is also important for understanding and modeling atmospheric flows, of relevance to weather prediction. The flows over complex terrain are currently poorly resolved in most atmospheric flow models and there is a need for improved predictive models. Better predictive models are also important for understanding flows in urban regions and wind farms.In this project, a series of high-fidelity computer simulations - to be carried out at Johns Hopkins in the US - and of physical experiments - to be performed at Southampton in the UK - will generate unprecedented data of flows over heterogeneous, multi-scale surfaces. Numerical modeling will be based on Large Eddy Simulation that uses a novel integral wall model implemented in a high-accuracy finite difference solver that uses sharp immersed boundary method to resolve larger-scale roughness elements. Three different cases will be considered both numerically and experimentally: (i) an abrupt change in nature of multi-scale roughness, (ii) finite patch of multi-scale roughness, and (iii) repeated changes in multi-scale roughness. The data will be analyzed and simulations and experiments compared. The experimental and numerical data as well as the physical insights obtained will be used to test existing, and develop new, analytical models that enable accurate prediction of drag and momentum transfers based only on available information about the topography of multi-scale heterogeneous surfaces. The project will strengthen graduate education, since the PhD student who will be a part of this project will gain substantial expertise in computational methods, modeling strategies and collaborating internationally with experimentalists. This training will be invaluable as these methodologies are widely recognized as areas of substantial growth in the coming decades, where experienced researchers will be most needed.

在几乎所有的工程和环境流中，湍流边界层（最接近给定表面的流程的一部分）处于粗糙墙状态。典型的例子包括在飞机和风力涡轮机叶片上发展表面不规则的边界层，宏观生物污染的船体，森林或风农场的边缘，城市檐篷，农作物边界，河床，河床以及在粗糙的海洋上。尽管进行了数十年的持续研究，但基于对表面的几何信息的动量转移和/或皮肤摩擦阻力的准确预测很困难。这主要是因为在大多数情况下，表面粗糙度的地形是多尺度的，也就是说，它包含多种粗糙度长度尺度。此外，粗糙度长度尺度和粗糙度特征的分布的变化在整个表面上是异质的。当前的预测方法主要是为均质和单尺度粗糙度元件分布而设计的，无法准确预测或提供对多尺度异质表面流动物理学的见解。在这项合作研究中，将采用一种系统的表征阻力和动量转移机制的系统方法，将采用异质多尺度表面的流动。这项研究将与许多行业广泛相关，在粗糙表面上流动至关重要。例如，在运输行业中，粗糙表面产生的阻力对运输效率及其环境足迹产生了重要影响。这项研究对于理解和建模与天气预测相关的大气流也很重要。在大多数大气流程模型中，复杂地形上的流量目前的分辨率很差，并且需要改善预测模型。更好的预测模型对于理解城市地区和风电场的流也很重要。在这个项目中，一系列高保真的计算机模拟 - 将在美国和实验的约翰霍普金斯（Johns Hopkins）进行，将在英国的南安普敦（Southampton）进行 - 将在英国的南安普敦（Southampton）进行 - 将会产生空前的多个多型，多种多样的多人surfaces surface。数值建模将基于大型涡流模拟，该模拟使用了在高准确的有限差求解器中实现的新型积分墙模型，该模型使用尖锐的沉浸边界方法来解决更大的粗糙度元素。三种不同的情况将在数值和实验上都被视为：（i）多尺度粗糙度的性质突然变化，（ii）多尺度粗糙度的有限斑以及（iii）多尺度粗糙度的重复变化。数据将进行分析，并比较模拟和实验。实验和数值数据以及所获得的物理见解将用于测试现有的现有，并开发新的，分析模型，从而仅基于有关多尺度异构表面的地形的可用信息来准确预测阻力和动量转移。该项目将加强研究生教育，因为将成为该项目的一部分的博士生将获得计算方法，建模策略并与实验者进行国际合作的实质性专业知识。这项培训将是无价的，因为这些方法在未来几十年中被广泛认为是实质性增长的领域，而经验丰富的研究人员最需要。