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

在非均匀表面和不同类型的粗糙度上的流动已经被广泛研究，主要是为了阻力目的。然而，对于流经地面升高的表面粗糙度的流动中发生的质量、动量、热量和相关阻力的传输知之甚少，这种粗糙度被称为e型粗糙度。这对许多工程应用至关重要，对太阳能光伏特别有意义。这是因为对流冷却在控制太阳能光伏发电效率方面起着至关重要的作用，在设计新的安装时，考虑到合适的风荷载是很重要的。该项目的目的是研究不同空间布置的地面表面粗糙度如何控制流动中的混合过程和流动结构。最终的问题是，是否有可能通过所建议的布置来操纵流动中的混合和阻力特性。该项目的结果将提高太阳能光伏的能量收集效率，从而直接影响太阳能社区，并帮助美国过渡到在更短的时间内实现碳中性的目标。该项目还将包括重要的教育活动，包括研究生的暑期交流计划，如何有效地向公众传播科学内容的培训，以及为太阳能社区开发培训视频。该项目的目标是对地面升高(e型)表面粗糙度和热跨距不均匀引起的扰动引起的混合过程有新的理解。这项研究的科学成果将包括加强目前与湍流和热力同时存在时发生在复杂表面上的混合过程有关的知识，并发展新的标度关系，其中包括加热和非加热光伏激发的地面升高表面粗糙度元素的影响。该项目的目标将通过协同工作来实现，包括创新的高分辨率大涡模拟(LES)和大规模风洞实验中的粒子图像测速。风洞实验将提供瞬时速度场，用于计算涡度收支，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，考虑到热效应。这一分析将有助于理解在高粗糙度元素中形成二次环流的因素。除了将在流体力学方面形成的新理解外，拟议的研究还将产生关键信息，以指导未来太阳能光伏发电场的设计。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.