Eulerian Multifluid Model of Hurricane Boundary Layer Laden with Polydisperse Ocean Spray

Accurate forecasting of hurricanes relies crucially on understanding of the fundamental physical processes governing these powerful storms. Mounting observational evidence and theoretical studies point to a strong influence of ocean spray on hurricane dynamics, which alters both vertical enthalpy and momentum fluxes in the marine atmospheric boundary layer. Our research reveals that these variations strongly depend on the size of spray droplets. Therefore, accounting for the distribution of droplet sizes is important to accurately describe and model the spray effect on hurricane characteristics.

We introduce Eulerian multifluid model, which treats air and spray droplets of different sizes as separate interacting turbulent continua, each described by its velocities, thermal and turbulent kinetic energies, and its own set of conservation equations for mass, momentum, and thermal and kinetic energies. The proposed approach reliably captures interactions among droplets of various sizes and their slip with respect to surrounding air that results in turbulence reduction. Additionally, the approach accurately represents turbulence attenuation caused by the droplet updraft by turbulent eddies against gravity.

Numerical solutions demonstrate the importance of accurate modeling of both spray size spectra and the correlation laws between wind speed and spray production intensity. The outcomes from the polydisperse model disclose distinct roles small and large spray droplets play in altering turbulent momentum and heat transport. The obtained results also illustrate significant quantitative differences between predictions made based on polydisperse and simplified monodisperse-spray approaches. These emphasize the importance of taking the droplet size distribution into account for accurate modeling of the influence of ocean spray on hurricane.

The authors acknowledge support by grants from the National Science Foundation, U.S.A. under Award No. 2302221