B143 気液乱流界面における物質輸送に与える界面活性物質の効果

抄録

Direct numerical simulation of turbulent mass transfer across a contaminated air-water interface is carried out. With increasing the Marangoni number, the thickness of the viscous sublayer in liquid is increased and the mean velocity profile converges to that near a solid wall. The tangential velocity fluctuations at the interface, however, have nonzero values even in a highly contaminated case, indicating that the velocity field near the interface is essentially different from wall turbulence. By decomposing the interfacial velocity vector into two components, i. e., irrotatioanl and solenoidal vectors, it is found that the irrotational motion is dumped significantly due to the surfactant, while the solenoidal motion kept almost unchanged. Since the irrotational motion at the interface plays a crucial role in the interfacial mass transfer, 40% decrease of the gas transfer rate is observed even in a slightly contaminated case.