The role of turbulent coherent structures on the evolving seabed

湍流相干结构对海底演化的作用

基本信息

批准号：
2242113
负责人：
Tian-Jian (Tom) Hsu
金额：
$ 38.09万
依托单位：
University of Delaware
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2023
资助国家：
美国
起止时间：
2023-05-15 至 2026-04-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2242113&HistoricalAwards=false
关键词：
role turbulent coherent structures evolving

项目摘要

Seabed bathymetric features, known as ripples, are responsible for hydrodynamic dissipation, sediment transport, and benthic flux exchange. The three-dimensional low steepness ripples commonly observed in medium and fine sand beaches (median grain size of 0.15-0.3 mm) have received much less attention compared to the high steepness coarse sand ripples, even though the medium and fine sand beaches are more common in nature. Furthermore, the migration of medium and fine sand ripples may contribute to a significant part of the beach profile evolution. The proposed work will apply numerical modeling methods to study medium and fine sand ripples driven by waves and currents. The Large Eddy Simulation (LES) two-phase flow methodology will be applied to understand the geometry and migration of medium-fine ripples in the presence of flow separation vortices, flow instabilities, and turbulent coherent structures in a turbulence-resolving system.Medium and fine sand ripples will be studied using a large-eddy simulation (LES) Eulerian two-phase methodology. The steepness of medium-fine sand ripples is both low and capricious, and it is hypothesized in this project that their evolution is dictated by flow instabilities and coherent structures such that the conventional paradigm which separates the primary vortices from the cascade of turbulent coherent structures is inadequate. The proposed work is expected to gain a new understanding of explaining the geometry and migration of medium and fine sand ripples, deliver an open-source numerical simulation model capable of simulating low steepness ripples, and inform improved parameterizations on transport rate and migration. The project will test the hypothesis that the Reynolds-averaged modeling approach that objectively separates the energy cascade of turbulent coherent structures from the resolved primary vortices becomes inadequate for low steepness ripples. This project will create the first turbulence-resolving (LES) Eulerian two-phase model capable of simulating the geometry and migration of medium and fine sand ripples by extending the existing open-source model, SedFoam.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.

海底测深特征（称为波纹）负责水动力耗散、沉积物输送和底栖通量交换。尽管中细沙滩更为常见，但与高陡度粗沙波纹相比，中细沙滩（中值粒径0.15-0.3毫米）中常见的三维低陡度波纹受到的关注要少得多在大自然中。此外，中型和细型沙纹的迁移可能对海滩剖面演变做出了重要贡献。拟议的工作将应用数值模拟方法来研究由波浪和水流驱动的中度和细度沙纹。大涡模拟 (LES) 两相流方法将用于了解湍流解析系统中存在流动分离涡流、流动不稳定性和湍流相干结构时中细波纹的几何形状和迁移。将使用大涡模拟 (LES) 欧拉两相方法研究细砂波纹。中细沙波纹的陡度既低又反复无常，在这个项目中假设它们的演化是由流动不稳定性和相干结构决定的，因此将初级涡旋与级联湍流相干结构分开的传统范式是不足。所提出的工作预计将对解释中细砂波纹的几何形状和迁移有新的理解，提供能够模拟低陡度波纹的开源数值模拟模型，并为改进传输速率和迁移的参数化提供信息。该项目将测试这样一个假设：雷诺平均建模方法客观地将湍流相干结构的能量级联与已解析的初级涡旋分开，对于低陡度波纹来说是不够的。该项目将通过扩展现有的开源模型 SedFoam，创建第一个湍流解析 (LES) 欧拉两相模型，能够模拟中细砂波纹的几何形状和迁移。该奖项反映了 NSF 的法定使命，并已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，认为值得支持。