Periodic Reporting for period 1 - GLITR (Breaking through: The Impact of Turbulence on the Gas-Liquid Interface)
Reporting period: 2022-09-01 to 2025-02-28
This project addresses an important gap in our scientific understanding: the factors that determine the rate at which gases, such as CO2 and O2, transfer from a gas phase to a liquid. This knowledge is critical for various environmental and engineering applications, such as gas exchange between the atmosphere and oceans, and the transfer of CO2 from flue gas to aqueous amines in carbon scrubbers.
Focusing on the air-water example, water, like air, consists of multiple molecules, not just H2O. For instance, the oceans store about 50% of all human-produced CO2, which was transferred there from the atmosphere. Additionally, the O2 cycle between the atmosphere and ocean is essential for supporting marine life. However, existing models of this gas exchange process can vary by more than 200%. While some of this variation is due to chemical processes and wave dynamics, turbulence also plays a significant role.
The GLITR project aims to develop a laboratory experiment where the turbulent properties of both water and air can be adjusted independently, allowing for unprecedented insight into this gas exchange process. This requires creating new measurement techniques to observe and quantify the physical processes involved. By achieving these goals, GLITR will provide detailed insights into gas transfer at a gas-liquid interface, enabling the development of predictive models that specifically account for turbulence’s role in momentum transfer and gas exchange between liquids and gases.
Focusing on the air-water example, water, like air, consists of multiple molecules, not just H2O. For instance, the oceans store about 50% of all human-produced CO2, which was transferred there from the atmosphere. Additionally, the O2 cycle between the atmosphere and ocean is essential for supporting marine life. However, existing models of this gas exchange process can vary by more than 200%. While some of this variation is due to chemical processes and wave dynamics, turbulence also plays a significant role.
The GLITR project aims to develop a laboratory experiment where the turbulent properties of both water and air can be adjusted independently, allowing for unprecedented insight into this gas exchange process. This requires creating new measurement techniques to observe and quantify the physical processes involved. By achieving these goals, GLITR will provide detailed insights into gas transfer at a gas-liquid interface, enabling the development of predictive models that specifically account for turbulence’s role in momentum transfer and gas exchange between liquids and gases.
GLITR's primary focus so far has been on experimental development. We have built a unique facility where wind flows over moving water, allowing for independent control of turbulence in both air and water using active grids. These active grids are devices positioned at the inlet of the wind and water channels, enabling us to adjust turbulence intensity and the size of eddies in the flow. Initial tests show an exceptional level of control over the system, which will enable us to explore gas-liquid momentum and gas transfer processes more deeply.
To measure these flows, we developed a novel synergy of measurement techniques. We use separate but simultaneous laser diagnostics to capture the velocity field in the water flow, the air-water interface, and the instantaneous gas concentration in the water. This setup allows us to observe an eddy formed at the air-water interface capture oxygen and transport it into the flow. Such detailed imaging of flows with deformable interfaces has not been possible before, and this capability marks a significant advance in our ability to understand transport processes at gas-liquid interfaces.
To measure these flows, we developed a novel synergy of measurement techniques. We use separate but simultaneous laser diagnostics to capture the velocity field in the water flow, the air-water interface, and the instantaneous gas concentration in the water. This setup allows us to observe an eddy formed at the air-water interface capture oxygen and transport it into the flow. Such detailed imaging of flows with deformable interfaces has not been possible before, and this capability marks a significant advance in our ability to understand transport processes at gas-liquid interfaces.
Our results thus far have shown that the rate at which O2 transfers from air to water can vary by 45% depending on the turbulence characteristics, even when all other flow properties and chemistry are kept constant. The findings also reveal that capillary waves play a secondary role to turbulence in this process within our laboratory experiment. This highlights the need to understand turbulence’s impact and to incorporate it into modeling tools.
It is worth noting that as waves approach breaking, the mechanics of the system will change, likely leading to different results. GLITR will also investigate the microbreaking regime as the project progresses to better understand this effect. These results were only possible due to the technological advancements in GLITR, including the development of a new facility and a novel synergy of measurement techniques, which have enabled us to explore the gas transfer process in unprecedented detail.
It is worth noting that as waves approach breaking, the mechanics of the system will change, likely leading to different results. GLITR will also investigate the microbreaking regime as the project progresses to better understand this effect. These results were only possible due to the technological advancements in GLITR, including the development of a new facility and a novel synergy of measurement techniques, which have enabled us to explore the gas transfer process in unprecedented detail.