Development of the sea-surface bursting layer model for microscopic evaluation of wind wave breaker effects on currents

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Experimental investigations using a wind-wave tank with a double deck, a sloping bottom and a computer-controlled wavemaker were made on the processes of momentum transfer from winds to currents through breaking waves and the turbulent structure of a bursting boundary layer with strong turbulence underneath water surface affected by wave breaking and air-flow separation. The obtained primary results are summarized as follows :1) Measurements using PIV and LDV demonstrated that the bursting boundary layer retaining the intensive turbulent kinetic energy and Reynolds stress is generated in near-surface area by breaking waves.2) The turbulent kinetic energy of the bursting layer exceeds about ten times of that of shear flow boundary layer caused by wind-induced current. The turbulent flow components within the bursting layer transmit about 30% of wind and breaker stresses acting on water surface to the water depth of about 7 times of H_<1/3>.3) A numerical simulation using the VOF method and the κ-ε model showed that the algebraic linear Reynolds stress model is applicable to the wave breaking processes except for the aerated bore front.4) The velocity of water surface currents driven by wind and breaker stresses is proportional to the wind speed but is independent of the occurrence of wave breaking.5) The values of turbulent kinetic energy and eddy viscosity coefficient within the bursting layer remarkably exceed those in the ordinary turbulent boundary layers underneath wind waves without breakers.