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，对于在地面隆起的表面粗糙度（称为e型粗糙度）上流动的质量动量、热量和相关阻力的传递，我们所知甚少。这对许多工程应用至关重要，对太阳能光伏发电尤为重要。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，在设计新装置时，考虑正确的风负荷是很重要的。该项目的目的是研究不同的地面高架表面粗糙度的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，是否有可能通过所提出的安排来操纵流动中的混合和拖动特性。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社区，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，包括研究生的夏季交流计划，如何有效地向公众传播科学内容的培训，以及为太阳能社区制作培训视频。该项目的目标是发展对混合过程的新认识，混合过程是由地面升高（e型）表面粗糙度和热展向非均质引起的扰动引起的。这项研究的科学成果将包括增强当前与复杂表面上的混合过程相关的知识，当湍流和热强迫同时存在时，会发生混合过程，并发展新的缩放关系，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创新的高分辨率大涡模拟（LES）和尺度风洞实验中的粒子图像测速等协同努力来实现。风洞实验将提供用于计算涡量预算的瞬时速度场，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，考虑热效应。这一分析将有助于理解在高粗糙度地层中形成二次循环的因素。除了在流体力学方面的新认识之外，拟议的研究还将产生指导未来太阳能光伏农场设计的关键信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.