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OCE-PRF: Vertical transport of buoyant, non-spherical particles in the wind-mixed ocean surface boundary layer

OCE-PRF：风混合海洋表面边界层中浮力非球形颗粒的垂直输送

基本信息

批准号：
2126193
负责人：
Lucia Baker
金额：
$ 29.65万
依托单位：
University of Washington
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2126193&HistoricalAwards=false
关键词：
OCE PRF Vertical transport buoyant

项目摘要

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Particles at the ocean surface are plentiful: microorganisms, ice crystals, debris, microplastics. Although many are buoyant, these particles do not passively float on the surface of the water; they are continually mixed within the upper regions of the ocean by the turbulence that results from wind blowing over the water surface. Unlike small, spherical particles, these non-spherical and sometimes large particles do not perfectly follow the fluid flow due to their size and shape, and their interaction with turbulence at the ocean surface is not well understood. The PI will conduct an experimental and analytical investigation to study how buoyant, non-spherical particles move, rotate, and disperse during wind-mixing at the surface of the ocean. Knowledge of how these particles behave will have far-reaching applications in ocean science, from ocean optics to plankton biology to sea ice dynamics. In particular, understanding the transport of non-spherical microplastic particles is critical for quantifying both the scale of microplastic pollution and its risks to human health and the environment. The results of this project will inform future policy, health guidelines, consumer behavior, and microplastic removal efforts. In addition, the PI will work to broaden participation in science within the local community through mentoring at the university level and involvement in extracurricular activities at the high school level. The PI will measure vertical transport and dispersion of non-spherical particles in a laboratory wind-mixed surface boundary layer using particle shadow tracking techniques. Experiments will be performed for a range of particle geometries and wind speeds relevant to the ocean surface layer. These measurements will then be used to develop an analytical model of particle spatial distribution over the water column. The project addresses a major gap in the current understanding of how particle shape and inertia affect particle transport in the wind-driven ocean surface layer. The Stokes number, a key parameter which quantifies how responsive a particle is to turbulent fluid motions, of particles in the ocean spans from zero to O(1), but most studies to date have focused only on particles with a Stokes number of zero, which perfectly trace the fluid flow. In addition to the Stokes number, other parameters that define the fluid-particle dynamics include the floatability parameter, the aspect ratio between the dimensions of non-spherical particles, and the particle Reynolds number. Non-spherical particle transport in the surface boundary layer spans a wide parameter space; however, systematic experimental studies throughout this parameter space have not yet been done. A complicating factor is that particle transport by turbulence is an inherently Lagrangian process, i.e., the relevant frame of reference is one that follows each particle along its trajectory. Lagrangian measurements which track particles in space and time are difficult to obtain in situ, and studies often describe particle transport and vertical concentration fields in an Eulerian frame of reference, i.e., within a stationary coordinate system. This project will systematically explore the parameter space of non-spherical, non-tracer particles in wind-driven turbulence and will obtain both Eulerian and Lagrangian statistics of particle concentration, depth, and orientation. The results will provide insights into the physical processes governing a wide range of ocean transport phenomena, including that of microplastic pollution.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.

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。海洋表面的微粒很多：微生物、冰晶、碎片、微塑料。虽然有许多是浮力的，但这些颗粒并不是被动地漂浮在水面上；它们在海洋的上层区域不断地混合，这是由风吹过水面所产生的湍流造成的。与小的球形颗粒不同，这些非球形颗粒，有时是大颗粒，由于它们的大小和形状，不能完美地跟随流体流动，而且它们与海洋表面湍流的相互作用还不是很清楚。PI将进行一项实验和分析调查，以研究浮力，非球形颗粒如何在海洋表面的风混合中移动，旋转和分散。了解这些粒子的行为将在海洋科学中有着深远的应用，从海洋光学到浮游生物生物学再到海冰动力学。特别是，了解非球形微塑料颗粒的运输对于量化微塑料污染的规模及其对人类健康和环境的风险至关重要。该项目的结果将为未来的政策、健康指南、消费者行为和微塑料清除工作提供信息。此外，该项目还将通过大学层面的指导和高中层面的课外活动，努力扩大当地社区对科学的参与。PI将使用粒子阴影跟踪技术测量实验室风混合表面边界层中非球形粒子的垂直传输和色散。将进行一系列与海洋表层有关的粒子几何形状和风速的实验。这些测量结果将用于开发水柱上颗粒空间分布的分析模型。该项目解决了目前对粒子形状和惯性如何影响风驱动海洋表层粒子运输的理解中的一个主要空白。斯托克斯数是量化粒子对湍流运动的反应程度的关键参数，海洋中粒子的范围从0到0(1)，但迄今为止，大多数研究都只关注斯托克斯数为0的粒子，它完美地追踪了流体的流动。除了Stokes数之外，定义流体-颗粒动力学的其他参数还包括可浮性参数、非球形颗粒尺寸之间的纵横比和颗粒雷诺数。非球面粒子在表面边界层中的输运跨越了很宽的参数空间；然而，在整个参数空间中尚未进行系统的实验研究。一个复杂的因素是，湍流中的粒子输运是一个固有的拉格朗日过程，也就是说，相关的参照系是跟随每个粒子沿着其轨迹的参照系。在空间和时间上跟踪粒子的拉格朗日测量很难在原位获得，研究通常在欧拉参照系中描述粒子的输运和垂直浓度场，即在固定坐标系内。本项目将系统探索风驱动湍流中非球形、非示踪粒子的参数空间，获得粒子浓度、深度和方向的欧拉和拉格朗日统计量。这些结果将为控制包括微塑料污染在内的广泛海洋运输现象的物理过程提供见解。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。