Two-fluid turbulent modelling of liquid CO2 dissolution in the ocean by LES

By using large-eddy simulation (LES) and the concept of two-fluid flow, the dissolution of liquid CO2 and turbulent diffusion of CO2 enriched seawater in vertical section of deep ocean were simulated to assess the physical impact of CO2 sequestration on the ocean in time period of several hours and space domain of hundred meters respectively. A set of filtered equations of N-S, mass, and scalars of seawater coupled with those of liquid CO2 droplets, in Eulerian-Eulerian formulation, were fully solved by means of finite volume scheme on the basis of the pressure correction principle of SIMPLEC. With the assumption of stably stratified turbulent flow, the turbulent flow field of seawater with horizontal shear flow was built up and maintained by a so-called forced-dissipative mechanism. The structure-function model was applied to treat vertical and horizontal components of sub-grid viscosity and diffusivity of seawater. For liquid CO2 droplet, the Smagorinsky's model was adopted. From the results obtained, we found: a). the turbulent flow and scalar diffusion fields were reasonably simulated for two fluids; b). with the exception of the CO2 releasing exit, there exists no observably interaction between plumes of liquid CO2 and CO2 enriched seawater because of the role of horizontal shear current. This means two separated plumes formed unlike the case without the current; c). the turbulent forcing intensity Plays a significant role on the formation of CO2 enriched seawater plume and on small-scale turbulent diffusion. The ratio of the vertical component of subgrid eddy diffusivity to that of the horizontal one was found to be 0.75 in the magnitude and 0.56 in turbulent kinetic energy.