崩壊する風波気液界面を通しての物質輸送に及ぼす気泡の影響

概要

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The effects of bubbles entrained into water by wave breaking on the mass transfer in wind-driven turbulence were experimentally and numerically investigated. The bubble entrainment rate and relative velocity between a bubble and liquid were measured using both a laser Doppler velocimeter (LDV) and a phase Doppler anemometer (PDA). The results show that the bubble entrainment rate increases linearly against wind speed and the relative velocity in wind-driven turbulence is smaller than the raising velocity of a bubble in the quiet water. Further, the mass transfer velocity for a bubble was estimated by means of a direct numerical simulation (DNS) over the wide range of the particle Reynolds number (0.1≤Re_p≤300). The DNS results show that the mass transfer coefficient for a bubble depends on Re_p but not on the ambient flow structure. It is also found that the contribution of the total bubbles to the total mass transfer across the breaking air-water interface is at most 7% in wind-driven turbulence.
2000-09-25