Direct numerical simulation of gas transfer through the air-water interface in a turbulent flow environment

• Applicant: Dr.-Ing. Herlina Herlina
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2007 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 53900148

Transfer processes of weakly soluble gases across the air-water interface plays a central role in many environmental and industrial systems. Reaeration in polluted rivers and the absorption of greenhouse gases, notably carbon dioxide into the ocean are two important examples of gas transfer processes in the environment. The difficulty in understanding the gas transfer problem of weakly soluble gases (O2, CO2, CO, NO, NO2) stems from the fact that the process is concentrated within a very thin layer on the liquid side (10-1000 µm). Most previous studies related the gas transfer rate to global measurable parameters. Recent development of advanced optical measurement techniques have provided better insight into the gas transfer problem. However, these techniques still have limitations in resolving the uppermost diffusive sublayer. The aim of this study is to improve the fundamental understanding of the physical mechanisms of gas transfer across the air-water interface in a turbulent flow environment using direct numerical simulations (DNS) by employing an adapted version of the LESOCC code developed at IfH. The DNS technique is highly suited for resolving the complex interaction between the molecular diffusion and turbulent processes near the interface including the uppermost diffusive sublayer. The project focuses on gas transfer processes across a shear-free interface with far-field homogenous turbulent water environment, such as generated by stream flows or grid-stirring. The results of the proposed DNS study aims to fill the gap in fundamental understanding that can not be resolved even with advanced laboratory experimental capabilities.

• DFG Programme: Research Grants