Cohesive Sediment Dynamics in Turbulent Flow

湍流中的粘性沉积物动力学

• 批准号: 1803380
• 负责人: Eckart Meiburg
• 金额: $ 30万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1803380&HistoricalAwards=false
• 关键词: Cohesive; Sediment; Dynamics; Turbulent; Flow

Cohesive sediment refers to particles below approximately 63 microns in size. It is present in ecologically sensitive environments such as rivers, lakes, estuaries, and fisheries. Reliable prediction of contaminant and nutrient transport in these environments requires accurate models of cohesive sediment dynamics. We currently lack such models. For the small particles in cohesive sediments, attractive forces between particles due to electric charges frequently dominate hydrodynamic and gravitational forces. While these attractive forces can cause the particles to form larger aggregates or "flocs", turbulent fluid stresses tend to break up the flocs. Hence, the size distribution of cohesive sediment flocs is governed by a delicate balance of interparticle and turbulent stresses, which affects their transport rates. The attractive forces between particles also strongly affect the erodibility of sediment deposits on the seafloor, which influences sediment transport processes in rivers and oceans. This research will explore cohesive sediment dynamics in turbulent environments via a series of computer models and simulations. The aim is to develop reliable, predictive tools for the transport of nutrients and contaminants in the environment. The results will also improve predictions related to other technologies, including deep sea hydrocarbon exploration. The research will educate and train a doctoral student, as well as undergraduate and high school students, in computational modeling, fluid dynamics, sediment transport, and high-performance computing.The proposed research explores the dynamics of cohesive sediment in turbulent environments via a series of increasingly complex computational investigations, based on a hierarchy of approaches ranging from one-way coupled, reduced-order Lagrangian point particle models to grain-resolving direct numerical simulations (DNS) that are fully `four-way' coupled. It will address a broad range of fundamentally important questions, among them: a) how do the turbulence properties affect the equilibrium balance between sediment flocculation/coalescence and break-up?, b) how does the floc size distribution vary as a function of the turbulence and sediment properties?, c) how does the effective settling velocity of the cohesive sediment depend on the turbulence and sediment properties?, d) how are the turbulence properties altered by the sediment?, e) how is the effect of cohesive sediment on turbulence different from that of non-cohesive sediment?, and f) how is the erodibility of a sediment bed affected by cohesive forces? The envisioned computational simulations will serve as basis for formulating scaling laws that capture the dynamics of cohesive sediment in turbulence, and which are suitable for implementation into existing larger-scale sediment transport 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.

粘性沉积物是指尺寸低于约 63 微米的颗粒。 它存在于河流、湖泊、河口和渔业等生态敏感环境中。对这些环境中污染物和养分传输的可靠预测需要准确的粘性沉积物动力学模型。 我们目前缺乏这样的模型。 对于粘性沉积物中的小颗粒，由于电荷而产生的颗粒之间的吸引力常常主导水动力和重力。虽然这些吸引力可以导致颗粒形成更大的聚集体或“絮凝物”，但湍流流体应力往往会破坏絮凝物。因此，粘性沉积物絮凝体的尺寸分布受颗粒间应力和湍流应力的微妙平衡控制，这会影响它们的传输速率。 颗粒之间的吸引力也强烈影响海底沉积物的侵蚀性，从而影响河流和海洋中的沉积物输送过程。这项研究将通过一系列计算机模型和模拟来探索湍流环境中的粘性沉积物动力学。 其目的是开发可靠的预测工具来运输环境中的营养物和污染物。 研究结果还将改进与其他技术相关的预测，包括深海碳氢化合物勘探。该研究将对计算建模、流体动力学、沉积物输送和高性能计算方面的博士生、本科生和高中生进行教育和培训。该研究通过一系列研究探索了湍流环境中粘性沉积物的动力学。日益复杂的计算研究，基于一系列方法，从单向耦合、降阶拉格朗日点粒子模型到完全“四向”耦合的晶粒解析直接数值模拟（DNS）。它将解决广泛的基本重要问题，其中：a）湍流特性如何影响沉积物絮凝/聚结和破碎之间的平衡平衡？，b）絮凝体尺寸分布如何随湍流和沉积物特性？, c) 粘性沉积物的有效沉降速度如何取决于湍流和沉积物特性？, d) 沉积物如何改变湍流特性？, e) 如何粘性沉积物对湍流的影响与非粘性沉积物不同？以及 f) 沉积物床的侵蚀性如何受到粘性力的影响？设想的计算模拟将作为制定尺度定律的基础，捕捉湍流中粘性沉积物的动力学，并且适合应用于现有的更大规模的沉积物输送模型。该奖项反映了 NSF 的法定使命，并被认为值得支持通过使用基金会的智力优点和更广泛的影响审查标准进行评估。

项目成果

An efficient cellular flow model for cohesive particle flocculation in turbulence

• DOI: 10.1017/jfm.2020.79
• 发表时间: 2020-01
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Kunpeng Zhao;B. Vowinckel;T. Hsu;T. Köllner;B. Bai;E. Meiburg

Halite Precipitation From Double‐Diffusive Salt Fingers in the Dead Sea: Numerical Simulations

死海双扩散盐指的石盐沉淀：数值模拟

• DOI: 10.1029/2019wr024818
• 发表时间: 2019
• 期刊: Water Resources Research
• 影响因子: 5.4
• 作者: Ouillon, Raphael;Lensky, Nadav G.;Lyakhovsky, Vladimir;Arnon, Ali;Meiburg, Eckart
• 通讯作者: Meiburg, Eckart