Collaborative Research: Experimental and Numerical Study of Bed Shear Stress and Turbulent Boundary Layer Structure Induced by Breaking-Wave-Generated Vortices

合作研究：破碎波产生涡流引起的床面剪应力和湍流边界层结构的实验和数值研究

• 批准号: 2049140
• 负责人: Morteza Derakhti
• 金额: $ 13.79万
• 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: 2021-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049140&HistoricalAwards=false
• 关键词: Collaborative; Research; Experimental; Numerical; Study

This research aims to improve the understanding of breaking wave vortices impinging on the seabed. This has broad impacts on the prediction of a wide range of near-shore processes where wave breaking is fundamental in driving the sediment transport and resulting morphological changes. Detailed laboratory experiments will provide a high quality, comprehensive data set to test and improve a numerical model to better resolve the effects of wave breaking and eddy impingement on the bottom boundary layer structure. In return, the validated model will provide more detailed information to help interpret the measured data as well as a valuable research tool to model prototype wave conditions not reproducible in the laboratory. This research project would benefit society by enabling the development of better engineering tools for coastal zone management and mitigation of coastal hazards. The project will support two PhD students, one at South Dakota State University (SDSU) and another at the University of Delaware (UD), and will provide an opportunity for the new PhD program at SDSU to grow through research collaboration with an established research center. The PhD student from UD will participate in a portion of the experimental program at SDSU and work with the SDSU PhD student on model/data comparison. He/she will also work for a period at the University of Washington (UW) during the development of needed model extensions. To broaden the impacts of the research on STEM education, the lead PI will design a new technical elective on advanced fluid mechanics laboratory, which will be offered to undergraduate seniors and graduate students. The course will include a suite of experiments to give students hands-on experience with measuring bed shear stresses in steady and unsteady flows using different experimental techniques and approaches, emphasizing the importance of careful experimentation and analysis to produce high-quality, reproducible results.The objective of this research is to understand the structure of the bottom boundary layer and determine the bed shear stresses induced by the impact of breaking-wave-generated vortices on a plane beach. Laboratory experiments will be conducted in a 25 m-long, 0.9 m-wide and 0.75 m-deep tilting flume equipped with a programmable wave generator. The turbulent velocity fields under spilling and plunging waves will be measured in a three-dimensional (3D) flow volume on smooth and rough beds using a volumetric three-component velocimetry (V3V) system. The measured data will be used to study the momentum balance in the near-bed region and to develop more accurate methods for estimating the bed shear stresses in the unsteady, non-equilibrium boundary layer associated with breaking waves. The measured data will also be used to validate a multi-phase (air-water) large eddy simulation (LES) scheme for breaking waves, already shown to accurately describe the processes of wave breaking and eddy formation and evolution, to better resolve eddy impingement on the bottom and resulting modifications to the boundary layer structure.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.

这项研究旨在提高对撞击海底的破碎波涡流的了解。这对预测各种近岸过程有广泛的影响，其中波浪破碎是驱动沉积物输运和由此产生的形态变化的基础。详细的实验室实验将提供高质量的综合数据集，以测试和改进数值模型，从而更好地解决波浪破碎和涡流冲击对底部边界层结构的影响。作为回报，经过验证的模型将提供更详细的信息，以帮助解释测量数据，以及一个有价值的研究工具，以模拟在实验室中无法重现的原型波浪条件。这一研究项目将有利于社会，使开发更好的工程工具，沿海区管理和减轻沿海灾害。该项目将支持两名博士生，一名在南达科他州州立大学（SDSU），另一名在特拉华州（UD）的大学，并将提供一个机会，在SDSU的新的博士课程通过与一个既定的研究中心的研究合作增长。来自UD的博士生将参加SDSU实验项目的一部分，并与SDSU博士生一起进行模型/数据比较。他/她还将在华盛顿大学（UW）工作一段时间，开发所需的模型扩展。为了扩大STEM教育研究的影响，首席PI将设计一个新的技术选修先进流体力学实验室，这将提供给本科生和研究生。该课程将包括一套实验，让学生使用不同的实验技术和方法测量定常和非定常流中的床面剪应力，强调仔细实验和分析的重要性，以产生高质量的，本研究的目的是了解底部边界层的结构，并确定由冲击引起的床面剪应力破碎波在平面海滩上产生的漩涡。实验室实验将在一个长25米、宽0.9米、深0.75米的倾斜水槽中进行，水槽配有可编程波浪发生器。在光滑和粗糙的床面上，使用体积三分量测速（V3 V）系统，在三维（3D）流动体积中测量溢出和倾伏波下的湍流速度场。测得的数据将用于研究近床区域的动量平衡，并开发更准确的方法，用于估算与破碎波相关的非稳定、非平衡边界层中的床面剪应力。测量数据还将用于验证多阶段（空气-水）大涡模拟（LES）破波方案已被证明能准确地描述波浪破碎和涡的形成与演化过程，以更好地解决底部的涡流冲击和由此产生的边界层结构的修改。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的学术价值和更广泛的影响审查标准。