NSF Award
2318816
A better understanding of exchange of momentum, heat, and mass at the ocean-atmosphere interface at very high wind speed is necessary to better predict extreme weather events, which have dramatic impact on human activities, such as tropical cyclone intensification. Given the complexity of these two-phase turbulent flows, modeling tools are extremely valuable to unravel the detailed physical mechanisms. This research will provide a novel computational framework for fully coupled air-water simulations at high wind speed, including breaking waves, turbulent wind, droplet generation and their influence on the heat and mass exchange in the turbulent wave boundary layer. The initial work on the small-scale dynamics of individual breaking waves and droplet evolution will feed into a larger-scale model able to resolve the flows that provide the forcing context for the small-scale model. This comprehensive approach will lead to a general improvement in simplified models and parameterization, that can be implemented and tested in a wide range of numerical tools, from high resolution models to larger scale Earth system models, leading to improvement in climate and weather forecast. This project will expose undergraduate and graduate students at Princeton to critical environmental challenges that require research on fundamental multi-phase flows, and promote the use of open-source methods, through workshop and teaching activities.<br/><br/>The large range of scales involved in air-sea interaction will be split into two sets of more tractable problems. The first will consider droplet evaporation in the air, fully resolving droplet ejection and heat exchange with the surrounding air for wind-wave breaking dynamics forced by turbulent boundary layer. Such high-fidelity simulations will span scales from 100 microns to 1m and focus on understanding the small-scale coupling between high wind forced turbulence close to the water surface and droplets, directly solving for heat and mass exchange, waves and droplets processes and the coupling of heat and momentum exchange at high wind speed. The models developed for these small-scale processes will be integrated into a multi-layer numerical framework, akin to large eddy simulations. Such simulations will be able to resolve realistic breaking wave statistics spanning scales from 1m to 1km, allowing to represent the outer scales of the turbulent flow. Analysis of the heat and momentum budget will help understand current uncertainties in bulk formulation and may lead to new parameterizations for the heat and drag coefficient applicable to larger scale models used for tropical cyclone intensification studies.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
