CAREER: Stratified Mixing in Sheared and Zero-Mean-Shear Turbulent Environments

职业：剪切和零平均剪切湍流环境中的分层混合

• 批准号: 2236654
• 负责人: Blair Johnson
• 金额: $ 50.07万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-04-01 至 2028-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2236654&HistoricalAwards=false
• 关键词: CAREER; Stratified; Mixing; Sheared; Zero

Mechanisms by which mass transport and mixing occur remain to be well-understood in flows for which there are interacting sources of energetic turbulence. The primary aim of this project is to evaluate various types of mass transport that occur from the interaction between mean shear stress (i.e. generated by velocity gradients in unidirectional flow) and instantaneous and localized shear stress generated by chaotic turbulence in the presence of density stratification. Findings from this work will improve understanding of deep ocean mixing, brine discharges in bays or subglacial lakes, saltwater intrusions in rivers, and avalanches, among others. The work will include mentorship of a graduate student and undergraduate researchers through the Graduates Linked with Undergraduates in Engineering program that supports women in STEM. The PI will develop large-scale public engagement events surrounding environmental mixing processes through art exhibits and educational modules. Further, the research team will partner with a local science museum to develop a permanent exhibit as well as a hands-on laboratory workshop for K-12 home-schooled students to study gravity currents; data generated from these experiments will be shared with the research community. The overarching goal of this research is to comprehensively evaluate the independent and combined roles of energetic turbulent flows with and without current-generated shear acting upon density-stratified fluid systems. This will be achieved via a comprehensive laboratory approach using unique and highly controllable facilities that allow full quantification of links between flow energetics, buoyancy, and fluid properties with mixing and mass transport dynamics. Three distinct flow scenarios will be considered: turbulence with no mean current, a density current released into fluid with background turbulence, and advection of turbulence over a density interface. Non-invasive quantitative imaging techniques will be used to measure velocity and mass concentration fields to characterize flow dynamics. This systematic approach will provide an understanding of how competing sources of turbulence contribute to mixing and transport, particularly when shear-driven flows act in conjunction with background turbulence. Impacts are expected to be far-reaching, with direct and practical means for implementing the scientific knowledge gained through the laboratory and synthesis efforts. Additionally, significant outcomes are expected via the complementary educational and public outreach activities designed to engage women and home-schooled K-12 students, along with the general public. These activities will be assessed annually throughout the duration of the proposal period to foster continued improvement of equity, diversity, and inclusivity in STEM.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.

在存在相互作用的能量湍流源的流动中，质量传递和混合发生的机制仍待充分理解。该项目的主要目的是评估平均剪切应力（即由单向流中的速度梯度产生）与存在密度分层的情况下混沌湍流产生的瞬时和局部剪切应力之间的相互作用而发生的各种类型的质量传递。这项工作的结果将增进对深海混合、海湾或冰下湖的盐水排放、河流中的咸水入侵以及雪崩等的了解。这项工作将包括通过支持 STEM 领域女性的“毕业生与本科生工程项目”项目对研究生和本科生研究人员进行指导。 PI 将通过艺术展览和教育模块围绕环境混合过程开展大型公众参与活动。此外，研究团队将与当地科学博物馆合作，开发一个永久性展览，并为 K-12 在家接受教育的学生提供一个实验室实践研讨会，以研究重力流；这些实验产生的数据将与研究界共享。这项研究的总体目标是全面评估有或没有电流产生的剪切作用于密度分层流体系统的高能湍流的独立和组合作用。这将通过使用独特且高度可控的设施的综合实验室方法来实现，这些设施可以全面量化流动能量、浮力和流体特性与混合和质量传递动力学之间的联系。将考虑三种不同的流动场景：没有平均电流的湍流、释放到具有背景湍流的流体中的密度电流以及密度界面上的湍流平流。非侵入性定量成像技术将用于测量速度和质量浓度场，以表征流动动力学。这种系统方法将有助于了解湍流的竞争源如何促进混合和传输，特别是当剪切驱动流与背景湍流共同作用时。预计影响将是深远的，具有直接和实用的手段来实施通过实验室和合成工作获得的科学知识。此外，旨在吸引女性和在家接受教育的 K-12 学生以及公众参与的补充性教育和公共外展活动预计将取得重大成果。这些活动将在整个提案期间每年进行一次评估，以促进 STEM 领域公平性、多样性和包容性的持续改善。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进行评估，被认为值得支持审查标准。