Spray droplet modeling: 2. An interactive Eulerian‐Lagrangian model of evaporating spray droplets

Abstract

This paper describes an imeractive Eulerian-Lagrangian model of the turbulent transport of evaporating droplets. A k-e (where k is turbulem kinetic energy and • is its rate of dissipation) turbulence closure model is used to accurately simulate stable, near-neutral, and unstable boundary layers within the large air-sea interaction tunnel at the Institut de M6canique Statistique de la Turbulence (IMST), Luminy, France. These results are then used with the Lagrangian model described in part 1 [Edson and Fairall, 1994]. The coupled model is shown to give excelleto agreemere with droplet dispersion measuremeres made during the 1988 Couche Limite Unidimensionelle Stationnaire d'Embrums (CLUSE, a French acronym that translates to one-dimensional stationary droplet boundary layer) campaign. Additionally, this paper describes how the coupled model can now be used to investigate the imeraction between the evaporating droplets and the turbulent fields of temperature and humidity. The investigation shows that although the influence of the droplets is small under the conditions simulated at IMST, the potential for substamial modification of the surface energy budget exists for high-wind conditions over the ocean. addresses some of the advantages of this combined (Eulerian plus Lagrangian) approach over separate approaches (Eulerian or Lagrangian) in simulations of the turbulent transport of heavy particles. It then concludes with the results from the interactive model for simulations of droplet dispersion in both a laboratory and marine atmospheric surface layer. Copyright 1996 by the American Geophysical Union. 2. Eulerian k-½ Model Paper number 95JC03280. 0148-0227/96/95JC-03280 $5.00 The Eulerian code used in this simulation is derived from a k-e model developed at the Laboratoire de M6canique des Fluids, 1279 1280 EDSON ET AL.: EULERIAN-LAGRANGIAN MODEL OF EVAPORATING SPRAY Ecole Centrale de Nantes, France, to simulate flows around urban structures [Ldvi Alvards et al., 1990; Ldvi Alvards and Sini, 1992; Lakehal et al., 1996]. In the atmospheric surface layer, expressions for the instantaneous velocity field for incompressible fluid flow can be written OU. ' -o (1) % act, act,__ • aa o•-o• r a• * c5 % p• a•, -•" *" ' (•) where Einstein's summation notation is used and the Boussinesq approximation has been applied, v is the kinematic viscosity; ©v is the ambient virtual potential temperature; gi = (0,0,-g) where g is the gravitational acceleration; and Pa and or• and virtual potential temperature of the reference state of the fluid, respectively [LandaM and Mollo-Christensen, 1986]. In (2) the pressure field P represents the departure from the reference pressure field in hydrostatic balance. In developing equations designed to study flows where the mean departure from hydrostatic equilibrium can be nonzero (e.g., around a building), Sini [1986] and Sini and Dekeyser [1987] decomposed this departure from hydrostatic equilibrium into mean and fluctuating parts. The Reynolds averaged equations for the mean variables are then...

SeaCluse: Numerical simulation of evaporating sea spray droplets

“…While these models successfully demonstrate certain characteristics of evaporating sea spray droplets, they do not include a description of the influence of the wave on the lower atmospheric layer. In particular, droplets enter the domain at the flat surface [Kepert et al, 1999] or at an elevated height related to the wave height [Edson et al, 1996]. As shown by Mestayer et al [1996], an explicit treatment of the wave-influenced surface layer reveals that the number of droplets present above the wave crests (measurable quantity) may significantly differ from the number of droplets entering the domain at the wavy surface (source function).…”

“…While this approach may be justified for small droplets, the authors acknowledge that their assumption limits the maximum particle size which can be treated in the model to ---30/•m. Edson et al [1996] take nonlinear effects explicitly into account using a Eulerian-Lagrangian approach, as do Kepert et al [1999] (improving on the Fairall et al [1994] approach) by solving height-dependent budget equations (with nonfixed droplet concentrations). While these models successfully demonstrate certain characteristics of evaporating sea spray droplets, they do not include a description of the influence of the wave on the lower atmospheric layer.…”

The impact of the hexos programme

“…By combining it with Eulerian models of the turbulent flow fields, Edson (1990) and Edson et al (1996) extended the Lagrangian approach to the simulation of spray droplet behaviour in nonhomogeneous flows. Mestayer et al (1995) extended the one-dimensional eddydiffusivity model to the description of a marine atmospheric surface layer in the presence of sea spray, including the effects of wave motion.…”

Coarse Aerosol Concentration Over the North Polar Waters of the Atlantic

“…Without precise determination of the flux of drop emission from the sea surface, it is not possible to ascertain whether sea spray affects the air-sea fluxes of heat and latent heat (Bortkovskij 1972(Bortkovskij , 1987Borisenkov 1973;Petelski 1986, 1996, Mestayer et al 1989Fairall et al 1990;Andreas 1992;Edson et al 1996). Mechanisms of sea salt particle transport from the sea surface to the atmosphere is well understood thanks to efforts of many researchers, such as Blanchard (1954Blanchard ( , 1963Blanchard ( , 1989 and Cipriano et al (1983).…”