PIV를 이용한 테일러 기포 주변의 속도장 측정

Abstract

Slug flow is found in a lot of industrial situations. Taylor bubble is a component of slug flow, so this bubble was became theme of many researches for two-phase flow. But most research have used liquid that has different flow properties from liquid using real industrial situation. Therefore flow aspect is derived from those researches has a limitation of applicability for air-water or steam-water two phase flow that is happened on industrial situation. Present CFD code for two-phase flow is capable to simulate Taylor bubble and flow aspect around that bubble in limited situation. For compensation of this limitation, this study deals with Taylor bubble rising in the vertical tube on air-water two-phase flow. This study is analysis of velocity and changing velocity for Taylor bubble and vicinity of rising Taylor bubble in stagnant liquid or co-current liquid. Experiments had conducted on raising Taylor bubble in stagnant liquid or co-current liquid. In assumption of Taylor bubble is symmetry, velocity field for Taylor bubble and vicinity of bubble was analyzed using right part of the bubble. As a result of analysis, it is possible to confirm previous research's founding that raising bubble in stagnant water affects 0.5 ~ 0.6 D from nose. Liquid in liquid film is decelerated at the boundary between body and tail. because of flow continuity. In the case of co-current flowing, a stagnant section appear as bubble rise. And that section was descent as superficial velocity of liquid was increased. But if superficial velocity of liquid could be faster than the fastest velocity of this experiment, the stagnant section will be ascend. At further work, PIV-PST(Pulsed Shadow Technique) system will be used for overcome PIV technique's limitation that was exposed in this experiment. And the development of processing algorithm will be conducted for post-processing of PIV analysis.