Large-Eddy Simulation of a Near-Surface Water Layer Laden With Microbubbles
摘要
We perform a large-eddy numerical simulation of a near-surface water layer laden with microbubbles having diameters less than 1 mm in the presence of a specified stationary surface wave in order to investigate the influence of the wave-induced turbulence on the bubble transport. The mathematical model employed is based on solving the three-dimensional equations of the waterphase motion, which are filtered over subgrid fluctuations, in the Eulerian formulation, and the Lagrangian equations of the bubbles motion. The turbulent-viscosity concept, where the kinetic energy of the pulsations unresolved by the calculation grid is determined by solving a prognostic equation, is used to close the subgrid stresses in the water velocity equation. The results show that the influence of the turbulence on the bubble transport leads to a reduction of the transfer of the bubbles, as compared to the Stokes drift, in the vicinity of the water surface, and an enhancement of the transfer in the water depth (i.e., turbulent diffusion of the bubble Stokes drift) occurs. The results also show that the turbulence does not affect significantly the vertical component of the concentration flux, which is controlled by the established bubble velocity in quiescent water.