Effect of microscopic interfacial structure on gas-liquid two phase flow and application for flow control.

气液界面上的质量、动量和能量的传递现象是气液两相流动的重要基础，并随界面条件的不同而发生剧烈的变化。例如，已知的是，表面活性剂的添加通过防止结合和降低气泡的上升速度而对包括液体中的气泡数量的泡状流的整个流动结构产生很大影响。本研究的目的是阐明表面活性剂存在液体的本体浓度与界面结构的关系，定量分析杂质对两相流宏观流动动力学的影响。为了研究超纯水和表面活性剂溶液在静止液体中的升泡现象，进行了超纯水和表面活性剂溶液在静止液体中的升泡实验，并利用Navier-Stokes方程和Marangoni效应对升泡过程进行了模拟。 ...更多信息 g静止水中半径为50 μ m ~ 1 mm的单个小气泡。证实了超纯水中上升气泡的雷诺数与阻力系数的关系与纯液体的理论关系相同。在数值模拟中，采用亨利型和朗缪尔型吸收模型，沿沿着气泡界面采用正交曲线坐标系，分析了表面活性剂对不可变形球形气泡上升阻力的影响。数值模拟结果表明，即使表面活性剂的加入量很小，Marangoni效应也能显著增加上升气泡的阻力，且对于相同直径和相同终端速度的气泡，Marangoni效应随雷诺数的增加而变得重要。此外，模拟显示分离涡与二次涡后面的气泡在表面活性剂溶液中上升，从来没有观察到在纯水中。少

Transport phenomena of mass, momentum and energy at gas liquid interface is most important basis for gas-liquid two phase flow and various drastically with interface condition. For example, it is known that additon of surfactant gives large influence on whole flow structure of bubbly flow which includes numbers of bubbles in liquid by preventing coalition and reducing rising velocity of bubbles. The purpose of this research is to clarify relation between bulk concentration of surfactant existing liquid and interfacial structure, and quantitative analysis of influence of impurity on macroscopic flow dynamics of two phase flow. Experiment of rising bubble in stationaly liquid by using ultra pure water and surfactant solution of known concentration, and simulation of rising bubble by using Navier-Stokes equation coupled with Marangoni effect were conducted to investigate mechanism of basic interfacial phenomena.In the experiment, behavior of the rising bubble was investigated by generatin … More g small single bubble of 50mum to 1mm in radius in stationary water. Relation between Reynolds number and drag coefficient for rising bubble in the ultra pure water was confirmed to be same as one derived from theory for pure liquid. Moreover, it was observed that addition of small amount of 3-pentanol into pure water reduces rising velocity significantly.In the numerical simulation, effect of surfactant on drag of rising bubble was analyzed for undeformable spherical bubble by adopting absorption model of Henry type or Langmuir type and by using orthogonal curvilinear coordinate system along bubble interface. As a result of numerical simulation, it was demonstrated that drag of the rising bubble can remarkably increase by Marangoni effect for even small amount of surfactant, and that the Marangoni effect becomes important with Reynolds number for bubbles having same diameter and same terminal velocity. Further, the simulation shows separating vortices associated with secondary vortices behind the bubble rising in surfactant solution, never observed in pure water. Less