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

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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