HR: 14:50h
AN: OS52G-04    [PDF]
TI: Numerical Investigation of Coupled Air-Water Turbulent Boundary Layers at Small Scales
AU: Hendrickson, K
EM: kelli@vfrl.mit.edu
AF: Massachusetts Institute of Technology, Dept. of Ocean Engineering, 77 Mass. Avenue, 5-321, Cambridge, MA 02139 United States
AU: Liu, S
EM: songliu@mit.edu
AF: Massachusetts Institute of Technology, Dept. of Ocean Engineering, 77 Mass. Avenue, 5-321, Cambridge, MA 02139 United States
AU: * Shen, L
EM: lshen@mit.edu
AF: Massachusetts Institute of Technology, Dept. of Ocean Engineering, 77 Mass. Avenue, 5-321, Cambridge, MA 02139 United States
AU: * Shen, L
EM: lshen@mit.edu
AF: Johns Hopkins University, Dept. of Civil Engineering, 3400 North Charles Street, Baltimore, MD 21218 United States
AU: Yue, D K
EM: yue@mit.edu
AF: Massachusetts Institute of Technology, Dept. of Ocean Engineering, 77 Mass. Avenue, 5-321, Cambridge, MA 02139 United States
AB: We consider the mechanisms of air-sea coupling at low wind speeds at small spatial scales. Numerical simulations of the air and water turbulent flows are performed with coupled free-surface boundary conditions. We consider two canonical problems: coupled air-water Couette flows with passive scalars and unsteady spilling breakers, to obtain useful insights into the structures and dynamics of turbulent flows in the vicinity of the air-sea interface. It is found that the flow structures at the air-water interface are mainly controlled by the underneath water motions. Surface features such as low-speed streaks and streamwise vortices are highly correlated with the coherent turbulence structures on the waterside. While the turbulent boundary layer on the airside resembles the boundary layer near a solid wall, the boundary layer on the waterside is qualitatively distinct from those near a solid wall or a shear-free free surface. It is also found that, in the presence of steep and spilling-breaking surface waves, there exists substantial vortex flux at the air-water interface. The surface vorticity is generated by two mechanisms: surface parallel velocity with a sharp change in interface curvature and work due to surface tension forces. Based on the extensive simulation datasets, we obtain statistics of scalar transport and turbulent kinetic energy budget in the coupled air-water boundary layer. It is found that the inviscid energy transport associated with surface waves has a magnitude much larger than the viscous transport. The interfacial transport process is dominated by the pressure forces.
DE: 4504 Air/sea interactions (0312)
DE: 4524 Fine structure and microstructure
DE: 4560 Surface waves and tides (1255)
DE: 4568 Turbulence, diffusion, and mixing processes
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting