Two-phase slug-to-annular flow pattern transition in microgravity

It has been established through the identification and evaluation of characteristic forces dominant in two-phase gas–liquid flow field that Suratman number is the key dimensionless group in slug–annular flow pattern transition under microgravity. Furthermore, the intrinsic physical mechanism underlying the transition has been explored with the aid of experimental results. It is revealed that slug–annular flow pattern transition depends on Suratman number and the ratio of superficial gas to liquid Reynolds numbers. This result provides a physical basis to the existing empirical transition equation which is based on the same two dimensionless groups.