Collaborative Research: Dust Entrainment Processes by Convective Vortices and Localized Turbulent Structures: Experimental and Numerical Study

合作研究：对流涡旋和局部湍流结构的粉尘夹带过程：实验和数值研究

• 批准号: 2207115
• 负责人: Yulia Peet
• 金额: $ 33.16万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2207115&HistoricalAwards=false
• 关键词: Collaborative; Research; Dust; Entrainment; Processes

Dust in the atmosphere plays a significant role in modulating weather, air quality, and climate. Most studies of the lofting of dust from the surface have focused on steady wind conditions. However, there are obvious examples of other types of dust lifting mechanisms, such as dust devils, that occur in situations where the wind flow is more complicated. This research project will combine high-resolution numerical modeling with laboratory experiments to study dust devils and convective vortices and how they entrain dust from the surface. The long-term impact of the project will be to improve the prediction of dust entrainment, which has a significant climate impact. The research team will also conduct a significant education and outreach effort, with graduate and undergraduate students, outreach to K-12 students, and a virtual mini-symposium including international partners. The project plans to enhance diversity through specific programs that recruit underrepresented undergraduate students.The primary objective of this project is to identify and characterize the fundamental mechanisms triggering the entrainment of dust in the non-equilibrium conditions that depart from a canonical, well-investigated scenario of a fully-developed boundary layer flow that assumes both spatial homogeneity and statistical stationarity. An example of a non-equilibrium condition is a dust devil, which is a vortical structure that can lift significant amounts of dust. The research team will, through a combination of laboratory experiments and numerical simulations, characterize and identify the role of individual dust lifting processes in the physics of sediment entrainment by dust devils and convective vortices. The laboratory experimental setup consists of a vortex generator with three-dimensional particle image velocimetry (PIV) and particle tracking velocimetry (3D-PTV) systems. The computational aspect of the project will use an open-source spectral-element method (SEM) code Nek5000 which was co-developed by one of the researchers. The laboratory and numerical techniques would be used to answer the following questions:1. What is the effect of a horizontal spatial inhomogeneity of mean and fluctuating properties of the carrier flow turbulence on dust entrainment mechanisms in non-canonical vortex flows? What is the role of the competing forces, such as aerodynamic, pressure gradient, cohesion, gravity and electric forces in the dust entrainment processes?2. What is the role of the particle size, Stokes number and the size distribution modality? Would the main mechanisms be different or similar for inertial particles of different sizes?3. What kind of agreement is expected between experimental and computational results in a representation of multiphase flow turbulence? What is the source and value of uncertainties?4. What are the implications for modeling? How well the global (local) sediment fluxes are correlated with the global (local) vortex flow variables? This information is critical for developing improved sediment flux parameterizations for simulation models.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.

大气中的灰尘在调节天气、空气质量和气候方面起着重要作用。 大多数关于尘埃从地表飘离的研究都集中在稳定的风条件下。 然而，还有其他类型的灰尘提升机制的明显例子，例如在风流更复杂的情况下发生的沙尘暴。 该研究项目将把高分辨率数值模拟与实验室实验相结合，研究沙尘暴和对流涡旋以及它们如何从地表夹带灰尘。 该项目的长期影响将是改善对粉尘夹带的预测，这对气候有重大影响。 研究团队还将开展重要的教育和推广工作，与研究生和本科生，K-12学生的推广，以及包括国际合作伙伴在内的虚拟小型研讨会。 该项目计划通过招收代表性不足的本科生的具体计划来增强多样性。该项目的主要目标是确定和表征在非平衡条件下触发粉尘夹带的基本机制，该非平衡条件偏离了假设空间均匀性和统计平稳性的充分发展的边界层流动的规范的、充分调查的场景。 非平衡条件的一个例子是尘暴，这是一种可以举起大量灰尘的漩涡结构。 该研究小组将通过实验室实验和数值模拟相结合的方法，描述和确定单个沙尘扬升过程在沙尘暴和对流涡流夹带沉积物的物理过程中的作用。 实验室的实验装置包括一个涡流发生器与三维粒子图像测速（PIV）和粒子跟踪测速（3D-PTV）系统。 该项目的计算方面将使用由其中一名研究人员共同开发的开源谱元法（SEM）代码Nek 5000。 实验室和数值技术将被用来回答以下问题：1。载流湍流的平均和波动特性的水平空间不均匀性对非正则涡旋流中尘埃夹带机制的影响是什么？在粉尘夹带过程中，空气动力、压力梯度、凝聚力、重力和电力等竞争力的作用是什么？2.粒度、斯托克斯数和粒度分布形态的作用是什么？对于不同大小的惯性粒子，其主要机制是不同的还是相似的？3.在多相流湍流的表示中，期望实验结果和计算结果之间有什么样的一致？不确定性的来源和价值是什么？4.对建模有什么影响？全球（局部）泥沙通量与全球（局部）涡旋流变量的相关性如何？该奖项反映了NSF的法定使命，并被认为值得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来支持。