A study on the bubble accumulation and coalescence phenomena in liquid and gas two-phase flow

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In this study, local measurements for the bubble accumulation and coalescence phenomena in a liquid-gas two-phase flow in a large diameter pipe were performed on flow parameters, such as void fraction, interfacial area concentration, bubble size, gas velocity, liquid velocity and turbulence intensity by using the local sensor techniques such as optical multi-sensor probes and hot-film probes and a database for the local flow parameters has been established. The experiment results show that the phenomenon can be attributed to the formation and development of large bubbles of pipe size. Based on the database, a drift flux model was newly developed for the flow evolving from bubbly to slug flows. The bubble accumulation and coalescence phenomena were numerically analyzed by using the one-dimensional two-fluid model with its interfacial drag model modified by including the present newly developed drift flux model. The numerical calculation predicted well the bubble accumulation and coalescence phenomena observed in the present experiments.