Yevgenii Rastigejev

This study investigates the mechanical and thermodynamic effects of the evaporating ocean spray on the structure and dynamics of a hurricane marine atmospheric boundary layer using Eulerian multifluid and mixture model approaches coupled with the E−ϵ turbulence closure. The multifluid framework treats air and spray as interpenetrating phases, enabling a physically consistent representation of air–droplet interactions governing momentum transfer, enthalpy exchange, and turbulence modulation. The mixture approach is based on a simplified description that captures only part of the underlying physics, yet offers an advantage in its ability to yield analytical insight. Mechanically, spray produces competing effects: on one hand, droplet inertia causes wind deceleration, on the other, the spray-induced turbulence attenuation, primarily resulting from the air–droplet friction, leads to strengthening the wind. Analytical and numerical results show that the latter effect prevails for typical spray droplet sizes leading to wind acceleration and drag reduction at hurricane wind speeds. Thermodynamically, evaporating droplets redistribute total heat flux in favor of its latent component, with effects strongly dependent on the droplet size. Small droplets suppress turbulence and reduce the total enthalpy flux, whereas large ones enhance it. Furthermore, spray significantly increases the total enthalpy-to-drag coefficient ratio with wind speed, which agrees with field observations.

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 Statement: Achieving 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.

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 multifluidE–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.

A detailed analysis of the evaporating ocean spray effect on the vertical latent and sensible heat fluxes in a marine atmospheric boundary layer (MABL) for different droplet sizes, vertical distributions of air temperature, humidity, and turbulent intensity is presented. For our analysis we have employed a two-temperature nonequilibrium MABL model developed in our previous work. The obtained analytical and numerical solutions show that the latent and total heat fluxes are significantly enhanced by large droplets because these droplets produce steep vertical gradients of moisture and air temperature in a MABL. Small droplets, however, do not noticeably change the total heat flux but rather redistribute the energy between its sensible and latent components. It has been shown that evaporating spray affects the turbulent kinetic energy (thus the intensity of the vertical turbulent transport) mostly mechanically by altering the vertical distribution of the mass density of the air–spray mixture rather than thermodynamically by changing vertical profiles of the air temperature and moisture. Furthermore, we have found that the vertical profiles of heat fluxes are approximately self-similar for a wide range of defining parameters, that is, can be approximately scaled to a reference heat profile for a wide range of vertical distributions of the temperature, humidity, and turbulence intensity. The obtained analytical expressions for the vertical heat fluxes affected by the spray presence enable their quick and efficient calculations. This will allow for the future construction of a computationally efficient spray and accurate parameterization to be used in global weather prediction models.

A non-equilibrium two-temperature multi-phase model of the atmospheric boundary layer above wave crests that is laden with evaporating ocean spray in high-wind condition is presented. The governing equations are derived from basic physical principles of conservation of momentum, mass and thermal energy in multiphase flows. The model derivation uses an Eulerian multifluid approach that considers spray as a continuous medium interacting with the gas phase. The E − ε turbulence closure is used. The developed theoretical framework accounts for the nonuniform ocean spray distribution and the thermal energy exchange between air and spray droplets that, in general, have different temperatures above the wave crest level. Such thermodynamic non-equilibrium conditions are shown to exist when the spray concentration is relatively low and the air humidity is far from saturation. The mechanical and thermodynamic effects of the evaporating spray on air flow and heat transport characteristics are obtained and sh... AbstractA non-equilibrium two-temperature multi-phase model of the atmospheric boundary layer above wave crests that is laden with evaporating ocean spray in high-wind condition is presented. The governing equations are derived from basic physical principles of conservation of momentum, mass and thermal energy in multiphase flows. The model derivation uses an Eulerian multifluid approach that considers spray as a continuous medium interacting with the gas phase. The E − ε turbulence closure is used. The developed theoretical framework accounts for the nonuniform ocean spray distribution and the thermal energy exchange between air and spray droplets that, in general, have different temperatures above the wave crest level. Such thermodynamic non-equilibrium conditions are shown to exist when the spray concentration is relatively low and the air humidity is far from saturation. The mechanical and thermodynamic effects of the evaporating spray on air flow and heat transport characteristics are obtained and sh...

High computational cost associated with numerical modeling of multi-scale global Atmospheric Chemical Transport (ACT) imposes severe limitations on the spatial resolution of fixed non-adaptive grids. Recently it has been shown that the interaction of numerical diffusion caused by the crude resolution with complex velocity field of atmospheric flows leads to large numerical errors. To address the described difficulties, we have developed Wavelet-based Adaptive Mesh Refinement (WAMR) method for numerical simulation of two-dimensional multi-scale ACT problems. The WAMR is an adaptive method that minimizes the number of grid points by introducing a fine grid only in the locations where fine spatial scales occur and uses high-order spatial discretization throughout the computational domain. The algorithm has been tested for several challenging ACT problems. Particularly, it is shown that the method correctly simulates dynamics of a pollution plume traveling on a global scale, producing less than 1% err...