Excellence in Research: The study of dynamics of an atmospheric boundary layer laden with polydisperse spray under high-wind conditions of a hurricane

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Predicting hurricane intensity is a very challenging task because it requires an in-depth understanding of complex multi-scale phenomena governing hurricane motion. Past research has demonstrated that the ocean spray effects on hurricane dynamics depend strongly on the size of spray droplets. Therefore, the PI will focus on developing a comprehensive mathematical framework and its numerical implementation to accurately model the polydisperse ocean spray effect on the vertical fluxes of momentum and heat in a hurricane boundary layer. This will aid in improving the accuracy of hurricane forecasts, which in turn will help minimize property damage and loss of human life. The research project will also allow North Carolina A&T State University, a state-supported HBCU, to sustain and expand recently established new research and educational capacity in applied mathematics and scientific computing with applications to atmospheric multiphase turbulent flows. Specifically, the PI will expand the currently existing mathematical model of a hurricane boundary layer laden with ocean spray by accurately accounting for spray polydispersity. The developed model will be used to conduct a comprehensive parametric study of its effect on the dynamics of the marine atmospheric boundary layer in high-wind hurricane conditions. To fill the current gap in understanding spray polydispersity's influence the PI plans to employ a modern theory of turbulent disperse multiphase flows and the Eulerian multi-fluid approach. This approach considers groups of droplets of different sizes, air, and water vapor as separate interacting turbulent continua, each described by its own set of conservation laws and characterized by its own velocity, temperature, and turbulent kinetic energy distributions. The conservation laws for polydisperse spray will be presented in the form of population balance equations. In particular, the method will consistently account for droplet breaking/coalescence and evaporation/condensation dynamics. Combining this method with a higher-order multi-fluid turbulence model will enable the PI to accurately predict the influence of polydisperse ocean spray on hurricane dynamics and structure.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.