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.

该项目的目的是开发一个模型，以实现WhiteCap持久性及其对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坏波数据包进行一系列比例模型实验室实验的结果。这项工作的动机在于，泡沫在气溶胶形成以及生物活性和气候相关的材料的海上运输中的关键作用。此外，泡沫的空中覆盖范围以一种或另一种方式隐含在波浪破裂和由此产生的空气交换过程中，这也取决于其持久性。将寻求以下关键问题的答案：1）可以使用高分辨率和高速摄影来确定由实验室在不同水平的表面活性剂浓度下产生的断裂波产生的白ecap泡沫的衰减时间？ 2）使用WhiteCap泡沫衰减数据以及实验室生成的波中气泡尺寸分布的测量源项，单个断裂事件产生的泡沫的演变是否可以建模？ 3）使用测量的WhiteCap覆盖范围和泡沫衰减速率的数据集，可以通过结合表面活性剂浓度对WhiteCap Foam衰减速率的影响来解释某些可观察到的可变性？实验室实验和现有海面图像的桌面分析的结合将用于收集WhiteCap FoAm Ampracking Waves的衰减时间的数据，以收集数据。实验室实验基于使用具有变化表面活性剂浓度的水在波通道中断裂波的观察。波浪，气泡羽和泡沫特性将受到监控，以使用波量规，向下看的摄像头俯冲和溢出断路器，以监视泡沫持久性，以及侧向外观的摄像头，以监视气泡羽状羽毛组成和深度。将测量总有机碳含量和水面张力，以捕获表面活性剂浓度对表面张力和WhiteCap泡沫衰减时间的影响。这些数据将驱动泡沫衰减的模型计算，并将与泡沫衰减时间和现有现场数据中的整体WhiteCap覆盖数据进行比较。智能优点：WhiteCap覆盖范围的测量提供了一个遥感工具，能够参数化一系列的空中海洋交换过程，例如空气气体煤气交换和初级海洋航空通道。当前的WhiteCap覆盖范围数据集之间的当前数量级散射可能部分是由于表面活性剂浓度的变化所致。表面活性剂浓度与泡沫稳定性之间的联系长期以来在泡沫物理学领域已知，但尚未在海洋学界明确探索。可以预料，与表面活性剂浓度相关的白卡普泡沫衰变时间的模型可以与白色固有覆盖范围的现场观察结合使用，以帮助解释白ecap覆盖范围内外的变化，也可以用作遥感的远程感应量的远程感应量。与气候相关的海洋过程，包括气溶胶的产生以及海面重要的表面活性化学物质的清除和浓度，这对云形成和大气化学具有影响。 WhiteCap泡沫生产和持久性的基于物理学的数学模型的开发将大大增强当前的遥感工具。波浪渠道研究期间产生的数据将在会议上介绍，并通​​过开放文献中的出版物与其他研究人员共享。对结果数据集的实验和分析将包括博士后研究人员的参与。此外，来自UCSD的本科实习生在院长和Stokes实验室工作将通过参加实验室调查来获得实验海洋学的经验。通过向公众沟通海洋科学研究的更大影响将通过Scripps（BAS）的桦木水族馆的教育计划来促进。 PIS将参与《海洋科学讲座》系列的BAS视角，每月的地球和海洋科学演讲者系列节目该系列为公众提供了专门为非专业观众设计的格式，可直接访问最新的科学。