Abstract:
A hybrid large-eddy simulation (LES) model is used to simulate the transport of oil droplet aerosols in wind over progressive water waves. The LES model employs a hybrid spectral and finite difference method of simulating the wind turbulence and a bounded finite-volume method for modeling the oil aerosol transport. Using a wave-following coordinate and computational grid, the LES model captures the turbulence flow and oil aerosol fields in the region adjacent to the unsteady wave surface. A pure wind-sea case with a flat surface and prescribed roughness and a swell wave case are considered to study the effects of swells on the transport of oil droplet aerosols with four different droplet diameters. This dataset supports the publication: Li, M., Zhao, Z., Pandya, Y., Iungo, G., & Yang, D. (2019). Large-Eddy Simulations of Oil Droplet Aerosol Transport in the Marine Atmospheric Boundary Layer. Atmosphere, 10(8), 459. doi:10.3390/atmos10080459
Suggested Citation:
Di Yang, Meng Li, Giacomo Valerio Iungo. 2020. Dataset for: Large-Eddy Simulations of Oil Droplet Aerosol Transport in the Marine Atmospheric Boundary Layer. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-45kq-6m91
Data Parameters and Units:
X [m], Y [m], Z [m], U [m/s], V [m/s], W [m/s], oil mass concentration [g/m^3], center of mass height [m]. Units for each file are detailed in the accompanying metadata description “dataset_description.pdf.”
Methods:
The computational domain is of size(L_x, L_y, H_0) = (600,400,100) m, with an open-sea condition and impose periodic velocity boundary conditions in the x- and y- directions, similar to many previous LES studies of the marine atmospheric boundary layer flow. The bottom of the simulation domain is bounded by the water surface. Two bottom conditions are considered in the current study. In the benchmark case, the bottom surface is kept flat and the effect of unresolved sea-surface waves are parameterized using the SGS sea-surface roughness height z_0. A typical open-sea value of z_0 = 2x10^(-4) m is used, in common with several previous LES studies. In the primary case of this study, a two-dimensional downwind swell wave train with wavelength 100 m and steepness 0.1 is imposed on the water surface, with the same SGS roughness as the benchmark case for the unresolved small scale waves. For a water depth of h=30m, the corresponding wave phase speed is c=12.2 m/s, and the wave period is T=8.2s. The wind flow is driven by an imposed streamwise pressure gradient corresponding to a friction velocity of u_* = 0.37 m/s and a characteristic wind speed of U_10 = 10 m/s at the 10m height for the benchmark case. In the swell wave case, the effective value of U_10 is smaller due to the additional pressure form drag induce by surface waves. The friction velocity u_* is set to be the same in both the flat and swell cases so that the turbulence statistics can be compared.
In this study, the air density is set to be 1.1845 kg/m^3, and the air viscosity is 18.444x10^(-6) kg/(mS). The oil droplet density is set to be rho_d = 895.5 kg/m^3. Four different droplet diameters are considered, i.e. d=2.5 um, 40 um, 60 um, and 100 um. The corresponding slip velocities are w_s = 1.6x10^-2) cm/s, 3.9 cm/s, 9.1 cm/s, and 21.4 cm/s, respectively. For each oil droplet size, the oil aerosols are released from 29 surface computational cells surrounding the point (x_0, y_0) = (42,0) m, with a total surface release area of 424.8 m^2 and a mass release rate of 1 g/s. The suspended oil droplets exit the simulation domain by deposition back to the water surface or through the downstream end of the domain via outflux condition.
View Metadata