Collaborative Research: Experimental and numerical studies of the effects of wind, wave scale, and salinity on bubble entrainment by breaking waves

本研究通过比例模型实验和计算流体动力学（CFD）模拟，研究了波浪尺度、波浪坡度、风强迫和盐度对破碎海浪中气泡产生和扩散的作用。这项工作的动机是气泡在与气候有关的海气交换中所起的关键作用，包括二氧化碳转移、气溶胶产生和海洋反照率。确定控制白浪中气泡夹带的物理过程及其对波浪尺度、波浪坡度、风强迫和盐度的依赖，将从根本上改变我们模拟海气相互作用的能力。目前仅有三组海洋白浪气泡数据集，显然不足以确定气泡夹带与环境强迫之间的基本物理联系。CFD模拟已经成为研究波浪破碎的有力工具，但可实现的长度尺度仍然比海洋白浪小几个数量级，而且重要的物理效应，包括盐度对气泡合并的影响、风强迫的作用和波浪尺度的影响，还没有得到充分的探索。用一个真实的海洋代理来验证波浪破碎的CFD模拟，将有助于它们用于研究海洋尺度交换过程，同时确定应该在哪些地方投入最大的努力，将数值模型扩展到相关的海洋过程。此外，实验数据将有助于改进气泡介导的海气交换过程的现有模型。还包括其他活动，以扩大项目的影响。参与的实验室有坚定的承诺，在广泛的社会范围内支持不同学术水平的研究和教育的整合。SIO pi将与斯克里普斯伯奇水族馆（BAS）的教育专业人士合作，增加STEM的参与度，扩大STEM职业的参与度。BAS和加州大学圣地亚哥分校CREATE STEM成功计划的工作人员将利用斯克里普斯海洋大气研究模拟器（SOARS）的资源共同设计、评估和实施体验式学习计划。为了解决STEM学习机会不平等以及BIPOC学生在地球科学领域代表性不足的问题，“探索海洋STEM职业”计划将吸引来自历史上被边缘化群体的中学生和高中生，并与合作伙伴合作，通过包括学术咨询和大学申请支持在内的服务来培养学生的兴趣和兴奋。此外，还包括资助两名暑期本科生实习生，以进一步学习海洋科学。Deane和Stokes将参加BAS外展车辆：海洋科学展望系列讲座。沈皮将领导开发一个用于气候和环境应用的水波计算机建模门户网站，作为向部落学院和大学、社区学院和少数民族服务机构的学生讲解地球科学的教材。门户网站将通过地球科学联盟传播，这是一个旨在扩大美国原住民参与地球科学的国家联盟。在三个规模和环境复杂性不断增加的波浪通道中进行的实验数据将与最先进的CFD计算进行比较，以研究气泡携带的流体动力学及其对环境参数的依赖。实验将利用最近委托的斯克里普斯海洋大气研究模拟器，该模拟器为风力驱动的海面提供了一个现实而可控的代理。CFD模拟将利用最新的算法进步，包括高保真气液界面捕获算法，该算法使用耦合水平集和流体体积方法，具有一致的质量和动量平流方案，最佳网络气泡识别和跟踪算法，以及自适应网格细化，以提供对破波峰内空气夹带过程和气泡行为的新见解。实验和模拟的协调将有助于验证CFD模型，推动进一步的算法和建模进步，并深入了解风驱动的海气界面上气泡介导的交换过程。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。

This is a study of the role of wave scale, wave slope, wind forcing, and salinity on the generation and dispersal of bubbles in breaking ocean waves through scale model laboratory experiments and computational fluid dynamics (CFD) simulations. The work is motivated by the critical role played by bubbles in climate-related air-sea exchanges, including CO2 transfer, aerosol production, and ocean albedo. Identification of the physical processes controlling bubble entrainment in whitecaps and their dependence on wave scale, wave slope, wind forcing, and salinity will fundamentally alter our ability to model air-sea interactions. At present, there are only three oceanic data sets of bubbles in whitecaps, which is obviously insufficient to determine any fundamental physical connection between bubble entrainment and environmental forcing. CFD simulations have become a powerful tool to study wave breaking but achievable length scales are still orders of magnitude smaller than oceanic whitecaps and important physical effects, including salinity effects on bubble coalescence, the role of wind-forcing, and the effects of wave scale, are not fully explored. Validating CFD simulations of wave breaking with a realistic ocean proxy will facilitate their use to study ocean-scale exchange processes while simultaneously identifying where the greatest effort should be directed to scale the numerical models to relevant oceanic processes. Moreover, data from the experiments will help improve existing models of bubble-mediated, air-sea exchange processes. Additional activities are included to broaden the impact of the project. The participating laboratories have a strong commitment to supporting the integration of research and education at various academic levels across a broad spectrum of society. SIO PIs will work with educational professionals at the Birch Aquarium at Scripps (BAS) to increase engagement in STEM and broaden participation in STEM careers. Staff at BAS and the CREATE STEM Success Initiative at UC San Diego will co-design, evaluate, and implement experiential learning programs using the resources of the Scripps Ocean Atmosphere Research Simulator (SOARS). To address inequities in access to STEM learning opportunities and under-representation of BIPOC students in the geosciences, the “Exploring Ocean STEM Careers” program will engage middle and high school students from historically marginalized groups and work with partners to build on students’ interest and excitement with services that include academic counseling and college application support. In addition, funding is included to support two summer undergraduate interns to further their education in marine science. PIs Deane and Stokes will participate in the BAS outreach vehicle: Perspectives on Ocean Science lecture series. PI Shen will lead the development of a portal of computer modeling of water waves for climate and the environment applications as teaching materials to illustrate Geosciences to students at tribal colleges and universities, community colleges, and minority serving institutions. The portal will be disseminated through the Geoscience Alliance, a national alliance for broadening participation of Native Americans in GeosciencesData from experiments in three wave channels of increasing scale and environmental complexity will be compared with state-of-the-art CFD computations to study the fluid dynamics of bubble entrainment and its dependence on environmental parameters. The experiments will leverage the recently commissioned Scripps Ocean-Atmosphere Research Simulator, which provides a realistic yet controllable proxy for the wind-driven sea surface. The CFD simulations will take advantage of recent algorithmic advances, including high-fidelity gas-liquid interface capturing algorithms using the coupled level-set and volume-of-fluid methods with consistent mass and momentum advection schemes, an optimal network bubble identification and tracking algorithm, and adaptive mesh refinement, to provide new insights into air entrainment processes and bubble behavior within breaking wave crests. Reconciliation of the experiments and simulations will enable verification of the CFD models, motivation for further algorithmic and modeling advances, and insights into bubble-mediated exchange processes across the wind-driven air-sea interface.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.