Collaborative Research: Transport and mixing processes in turbulent boundary layers over ground-elevated surface roughness

合作研究：地表粗糙度上湍流边界层的传输和混合过程

• 批准号: 2235751
• 负责人: Raul Cal
• 金额: $ 27.87万
• 依托单位: Portland State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-04-01 至 2026-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2235751&HistoricalAwards=false
• 关键词: Collaborative; Research; Transport; mixing; processes

Flows over heterogeneous surfaces and over different types of roughness have been extensively studied primarily for drag purposes. However, very little is known about the transport of mass momentum, heat and associated drag occurring in flows over ground-elevated surface roughness, named e-type roughness. This is critical for numerous engineering applications and of particular interest in solar photovoltaics. This is because convective cooling plays a critical role in controlling solar photovoltaics efficiency, and accounting for the right wind loads is important when designing new installations. The goal of this project is to investigate how different spatial arrangements of the ground-elevated surface roughness control mixing processes and flow structures in the flow. The ultimate question is whether it is possible to manipulate the mixing and drag characteristics in the flow through the proposed arrangements. Results of this project will enhance solar photovoltaics energy harvesting efficiency, thereby directly impacting the solar energy community and helping transition the U.S. into meeting the goal of becoming carbon neutral in a shorter period of time. The project will also encompass significant educational activities, including summer exchange programs for the graduate students, training on how to effectively communicate science content to the general public, and the development of training videos for the solar energy community.The goal of this project is to develop new understanding about mixing processes that result from the perturbations induced by ground-elevated (e-type) surface roughness and thermal spanwise heterogeneities. The scientific outcomes of this research will include enhancement of the current knowledge related to mixing processes over complex surfaces taking place when both turbulence and thermal forcings are simultaneously present and development of new scaling relations that include the effect of heated and non-heated photovoltaics-inspired ground-elevated surface roughness elements. The objectives of this project will be fulfilled through a synergistic effort including innovative high-resolution large-eddy simulations (LES) and particle image velocimetry in scaled wind tunnel experiments. The wind tunnel experiments will provide instantaneous velocity fields which will be used to compute the budget of vorticity, thus quantifying the momentum exchanges. The LES will also provide the instantaneous temperature fields which will also contribute to the balance, accounting for thermal effects. This analysis will facilitate understanding the factors contributing to the formation of secondary circulations in elevated roughness elements. In addition to the new understanding that will be developed in fluid mechanics, the proposed research will also yield critical information to guide the design of future solar photovoltaic farms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

人们对非均质表面和不同类型粗糙度上的流动进行了广泛的研究，主要用于阻力目的。然而，人们对地面高程表面粗糙度（称为 e 型粗糙度）上流动中发生的质量动量、热量和相关阻力的传递知之甚少。这对于许多工程应用至关重要，尤其是太阳能光伏发电。这是因为对流冷却在控制太阳能光伏发电效率方面发挥着关键作用，并且在设计新装置时考虑正确的风荷载非常重要。该项目的目标是研究地面高程表面粗糙度的不同空间排列如何控制流动中的混合过程和流动结构。最终的问题是是否可以通过所提出的布置来操纵流动中的混合和阻力特性。该项目的成果将提高太阳能光伏发电的能量收集效率，从而直接影响太阳能界，并帮助美国在更短的时间内实现碳中和的目标。该项目还将包括重要的教育活动，包括研究生暑期交流计划、如何向公众有效传播科学内容的培训以及为太阳能界开发培训视频。该项目的目标是对地面高程（e 型）表面粗糙度和热展向异质性引起的扰动产生的混合过程有了新的认识。这项研究的科学成果将包括增强当前与湍流和热力同时存在时发生的复杂表面混合过程相关的知识，以及开发新的尺度关系，其中包括受热和非受热光伏启发的影响地面高程表面粗糙度元素。该项目的目标将通过协同努力来实现，包括在规模化风洞实验中创新的高分辨率大涡模拟（LES）和粒子图像测速。风洞实验将提供瞬时速度场，用于计算涡度预算，从而量化动量交换。 LES 还将提供瞬时温度场，这也将有助于平衡，解释热效应。该分析将有助于了解导致粗糙度升高的元素中形成二次环流的因素。除了流体力学方面的新认识外，拟议的研究还将产生指导未来太阳能光伏发电场设计的关键信息。该奖项反映了 NSF 的法定使命，并通过使用基金会的评估进行评估，被认为值得支持。智力价值和更广泛的影响审查标准。