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Abstract The Eulerian multifluid mathematical model is developed to describe the marine atmospheric boundary layer laden with sea spray under the high-wind condition of a hurricane. The model considers spray and air as separate continuous interacting turbulent media and employs the multifluid E –ϵ closure. Each phase is described by its own set of coupled conservation equations and characterized by its own velocity. Such an approach enables us to accurately quantify the interaction between spray and air and pinpoint the effect of spray on the vertical momentum transport much more precisely than could be done with traditional mixture-type approaches. The model consistently quantifies the effect of spray inertia and the suppression of air turbulence due to two different mechanisms: the turbulence attenuation, which results from the inability of spray droplets to fully follow turbulent fluctuations, and the vertical transport of spray against the gravity by turbulent eddies. The results of numerical and asymptotic analyses show that the turbulence suppression by spray overpowers its inertia several meters above wave crests, resulting in a noticeable wind acceleration and the corresponding reduction of the drag coefficient from the reference values for a spray-free atmosphere. This occurs at much lower than predicted previously spray volume fraction values of ∼10 −5 . The falloff of the drag coefficient from its reference values is more strongly pronounced at higher altitudes. The drag coefficient reaches its maximum at spray volume fraction values of ∼10 −4 , which is several times smaller than predicted by mixture-type models.
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Polydisperse Sea Spray Effect on the Vertical Momentum Transport in Hurricanes
Abstract This study focuses on the influence of the sea spray polydispersity on the vertical transport of momentum in a turbulent marine atmospheric boundary layer in high-wind conditions of a hurricane. The Eulerian multifluid model treating air and spray droplets of different sizes as interacting interpenetrating continua is developed and its numerical solutions are analyzed. Several droplet size distribution spectra and correlation laws relating wind speed and spray production intensity are considered. Polydisperse model solutions have confirmed the difference between the roles small and large spray droplets play in modifying the turbulent momentum transport that have been previously identified by monodisperse spray models. The obtained results have also provided a physical explanation for the previously unreported phenomenon of the formation of thin low-eddy-viscosity “sliding” layers in strongly turbulent boundary layer flows laden with predominantly fine spray. Significance StatementAchieving better accuracy in hurricane forecasts requires an in-depth understanding and accurate modeling of the ocean spray effect on the vertical fluxes of momentum and heat in a hurricane boundary layer. It has been shown that this effect depends on the size distribution of spray droplets, also known as spray polydispersity. This study aims to investigate the influence of a polydisperse spray on the vertical momentum transport within hurricane boundary layers by employing a modern theory of turbulent disperse multiphase flows.
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- Award ID(s):
- 2302221
- PAR ID:
- 10522225
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of the Atmospheric Sciences
- Volume:
- 81
- Issue:
- 7
- ISSN:
- 0022-4928
- Format(s):
- Medium: X Size: p. 1127-1146
- Size(s):
- p. 1127-1146
- Sponsoring Org:
- National Science Foundation
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