Understanding the influence of surfactants on characteristic whitecap foam decay times

了解表面活性剂对白帽泡沫特征衰减时间的影响

• 批准号: 1155123
• 负责人: Grant Deane
• 金额: $ 72.04万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1155123&HistoricalAwards=false
• 关键词: Understanding; influence; surfactants; characteristic; whitecap

The goal of this project is to develop a model for whitecap persistence and its sensitivity to surfactants. The model will be based on a mathematical description of foam physics and the results of a series of scale-model laboratory experiments using seawater and breaking wave packets. The motivation for this work lies in the critical role foam plays in aerosol formation and the sea-to-atmosphere transport of biologically active and climatically relevant material. Moreover the aerial coverage of foam, which in one way or another is implicit in remote sensing of wave breaking and resulting air-sea exchange processes, also depends critically on its persistence. Answers to the following key questions will be sought: 1) Can high resolution and high speed photography be used to determine the decay times for whitecap foam produced by laboratory generated breaking waves under different levels of surfactant concentration? 2) Using the whitecap foam decay data coupled with measured source terms for the bubble size distributions within laboratory generated waves, can the evolution of foam produced by a single breaking event be modeled? 3) Using datasets of measured whitecap coverage and foam decay rates, can some of the observed variability be accounted for by incorporating the effects of surfactant concentration on whitecap foam decay rates?A combination of laboratory experiments and desktop analysis of existing sea surface images will be used to gather data on the decay time of whitecap foam produced by breaking waves. The laboratory experiments are based on observations of breaking waves in a wave channel using water with variable surfactant concentration. Wave, bubble plume and foam characteristics will be monitored for plunging and spilling breakers using wave gauges, a downward looking camera to monitor foam persistence, and a sideward looking camera to monitor bubble plume composition and depth. Total organic carbon content and water surface tension will be measured to capture the effects of surfactant concentration on surface tension and whitecap foam decay times. These data will drive model calculations of foam decay and will be compared with foam decay times and overall whitecap coverage data from existing field data.Intellectual Merit: Measurement of whitecap coverage provides a remote sensing tool capable of parameterizing a range of air-sea exchange processes such as air-sea gas exchange and primary marine aerosol flux. The present order of magnitude scatter between recent whitecap coverage datasets may in part be due to variations of surfactant concentration. The link between surfactant concentration and foam stability has long been known in the field of foam physics but has not yet been explicitly explored in the oceanographic community. It is anticipated that a model for whitecap foam decay times that is related to surfactant concentration could be used in conjunction with field observations of whitecap coverage to help explain variations within and between datasets of whitecap coverage and also as a remote sensing tool to determine surfactant concentration.Broader Impacts: The formation of surface foams by breaking waves in the open ocean play a critical role in a number of climate-related oceanic processes including aerosol production and the scavenging and concentration of important surface active chemicals at the sea surface, which have implications for cloud formation and atmospheric chemistry. The development of a physics-based mathematical model of whitecap foam production and persistence will greatly enhance current remote sensing tools. The data generated during the wave channel study will be presented at conferences and shared with other researchers through publication in the open literature. The experiment and analysis of the resulting data sets will include the participation of a postdoctoral researcher. In addition, undergraduate interns from UCSD working in the Deane and Stokes laboratories will gain experience in experimental oceanography by participating in the laboratory investigations. Broader impacts through communicating ocean science research to the public will be facilitated through the educational program at the Birch Aquarium at Scripps (BAS). The PIs will participate in the BAS Perspectives on Ocean Science lecture series, a monthly earth and ocean science speaker series the provides the public with direct access to up-to-date science in a format specifically designed for a non-specialist audience.

这个项目的目标是开发一个模型，白顶的持久性和表面活性剂的敏感性。该模型将基于泡沫物理学的数学描述以及使用海水和破碎波包进行的一系列比例模型实验室实验的结果。这项工作的动机在于泡沫在气溶胶形成和生物活性和气候相关材料的海洋到大气层的传输中发挥的关键作用。此外，泡沫的空中覆盖范围也主要取决于其持久性，而泡沫在某种程度上隐含在对波浪破碎及其造成的海气交换过程的遥感中。将寻求以下关键问题的答案：1）高分辨率和高速摄影是否可以用来确定在不同水平的表面活性剂浓度下由实验室产生的破碎波产生的白顶泡沫的衰减时间？2)使用白顶泡沫衰减数据加上测量源项的气泡尺寸分布在实验室产生的波浪，可以模拟泡沫的演变由一个单一的破碎事件？3)使用测得的白顶覆盖率和泡沫衰减率的数据集，可以通过将表面活性剂浓度对白顶泡沫衰减率的影响来解释观察到的一些变化吗？将利用实验室实验和对现有海面图像的桌面分析相结合的方法，收集关于破碎波浪产生的白顶泡沫衰减时间的数据。实验室实验的基础上，使用水与可变表面活性剂浓度的波浪通道中的破碎波的观察。波浪、气泡羽流和泡沫特性将使用波浪测量仪、下视摄像机和侧视摄像机进行监测，以监测泡沫持久性和气泡羽流成分和深度，从而监测倾翻和溢出破碎机。将测量总有机碳含量和水表面张力，以获取表面活性剂浓度对表面张力和白顶泡沫衰减时间的影响。这些数据将推动泡沫衰减的模型计算，并将与泡沫衰减时间和现有实地数据的总体白顶覆盖率数据进行比较。最近的白顶覆盖数据集之间的本数量级分散可能部分是由于表面活性剂浓度的变化。表面活性剂浓度和泡沫稳定性之间的联系在泡沫物理学领域早已为人所知，但在海洋学界尚未明确探讨。预计与表面活性剂浓度有关的白顶泡沫衰减时间模型可与白顶覆盖率的实地观测结合使用，以帮助解释白顶覆盖率数据集内和数据集之间的变化，并作为遥感工具确定表面活性剂浓度。在开阔的海洋中，波浪破碎形成的表面泡沫在许多气候变化中起着关键作用，相关的海洋过程，包括气溶胶的产生以及重要的表面活性化学品在海面的清除和浓缩，这对云的形成和大气化学有影响。开发一个关于白顶泡沫产生和持久性的基于物理学的数学模型，将大大加强现有的遥感工具。在波通道研究过程中产生的数据将在会议上展示，并通过公开文献与其他研究人员分享。实验和分析所产生的数据集将包括博士后研究人员的参与。此外，在迪恩和斯托克斯实验室工作的UCSD本科实习生将通过参与实验室调查获得实验海洋学方面的经验。通过向公众传播海洋科学研究，将通过斯克里普斯桦树水族馆（BAS）的教育计划促进更广泛的影响。PI将参加BAS海洋科学系列讲座，这是一个每月一次的地球和海洋科学演讲系列，以专门为非专业观众设计的形式为公众提供直接获取最新科学的机会。