Mixed Convection Gas Transfer across Surfactant-Contaminated Air/Water Interfaces

项目编号：cts -0500155项目负责人：John saylor联合单位：克莱姆森大学项目名称：混合对流气体在表面活性剂污染的空气/水界面上的传输该项目是化学和运输系统部门收到的一份主动提交的提案，由热传输和热处理项目资助。在淡水湖的空气/水界面上，溶解气体的转移对许多生态系统至关重要。保护这些生态系统需要了解这种界面气体交换问题。虽然对海洋典型的高风速条件下空气/水界面的气体交换进行了大量研究，但对湖泊常见的低风速条件的研究却很少。拟议的研究旨在解决这一关键需求，重点关注在强迫对流和自然对流都起作用的低风速条件下溶解气体（如氧气和二氧化碳）的运输；一种称为混合对流的输送状态。这项研究还将关注气体传递如何受到被称为“表面活性剂单层”的单分子厚有机薄膜的影响，这种薄膜在湖泊中无处不在。这项研究将包括一系列利用风洞/水洞的实验室实验，在那里，溶解气体（如氧气和二氧化碳）的转移将被测量为风速和空气-水温差的函数。表面活性剂污染对运输的影响将通过在水面上以受控的方式引入这些表面活性剂来量化。研究人员将利用流动可视化技术，包括对水面的红外成像和对地下流动的激光诱导荧光成像，来研究导致所观察到的气体交换现象的流体流动结构。拟议的研究将改进人类活动对湖泊影响的模型，更准确的全球气候变化模型，并提高许多工业过程的效率。

National Science FoundationABSTRACTProposal Number: CTS-0500155Principal Investigator: John SaylorAffiliation: Clemson University Proposal Title: Mixed Convection Gas Transfer Across Surfactant-Contaminated Air/Water InterfacesThis proposal was received as an unsolicited submission to the Chemical and Transport Systems Division and was funded by the Thermal Transport and Thermal Processing Program. The transfer of dissolved gases across the air/water interface of freshwater lakes is critical to numerous ecosystems. Protection of these ecosystems requires an understanding of this interfacial gas exchange problem. While there is a large body of research on gas exchange across air/water interfaces at the high wind speed conditions typical of oceans, little has been done to study the low wind speed conditions that are common on lakes. The proposed research seeks to address this critical need, focusing on the transport of dissolved gases such as oxygen and carbon dioxide, under low wind speed conditions where both forced convection and natural convection play a role; a transport regime referred to as mixed convection. This research will also focus on how gas transfer is affected by the single molecule thick organic films called 'surfactant monolayers', which are ubiquitous on lakes. The research will consist of a set of laboratory experiments utilizing a wind/water tunnel where the transfer of dissolved gases such as oxygen and carbon dioxide will be measured as a function of wind speed and air-water temperature difference. The effect of surfactant contamination on transport will be quantified by introducing these surfactants on the water surface in a controlled fashion. The fluid flow structures responsible for the observed gas exchange phenomena will be investigated using flow visualization techniques, including infrared imaging of the water surface and laser induced fluorescence imaging of the subsurface flow. The proposed research will result in improved models of the effect of human activity on lakes, more accurate global climate change models, and improvements in the efficiencies of numerous industrial processes.