Turbulence, Bubbles, and Drift Current in the Near-Surface Layer of the Ocean

Computational fluid dynamics (CFD) software has been applied to simulate the effects of bubbles on the dynamics of the near-surface layer of the ocean. Wave breaking was simulated via injection of turbulent jets containing a spectrum of bubble sizes. The CFD model appears to be a convenient tool for analyzing the effects of buoyancy due to presence of bubbles on the near surface turbulence and drift current. Results of numeric simulations are validated with the near-surface turbulence and air-fraction data obtained during TOGA COARE and GasEx-98. During these field campaigns, an electromagnetic fluctuation velocity sensor, conductivity sensor, and pressure sensor were mounted on the bow of the vessel. Estimates of the dissipation rate of turbulent kinetic energy and air-fraction in the near-surface layer of the ocean were made for wind speeds of up to 18 m/s and significant wave height of up to 4 m. The effective depth of the bubble penetration, as determined from air-fraction data, varied from 10% to 40% of the significant wave height. Implications of the numeric simulations for the surface drift velocity in hurricane conditions will also be discussed.