Local interfacial parameter distribution for two-phase flow under rolling conditions using a four-sensor optical probe

As a typical marine condition, rolling motion has a significant effect on a two-phase flow system, which has attracted increasing attention. However, the local characteristics of a two-phase flow system in rolling motion are seldom reported, which makes the two-fluid model difficult to apply in such a situation. More information that involves local interfacial parameters is required for further comprehending the intrinsic mechanism by which the interfacial area transport equation becomes applicable under a rolling condition. An experimental investigation of two-phase flow in a rolling condition was conducted by using a four-sensor optical probe. Parameters such as the local void fraction, interfacial area concentration (IAC) and bubble frequency were obtained. To obtain interfacial parameters at a rolling angle position, the averaged values in a small angle interval around the chosen position were used to represent the local parameters at that site, and in the same way, one can obtain variations of all of those parameters over a complete rolling cycle. The experimental results showed that the void fraction, IAC and bubble frequency present a periodic variation with the rolling motion. Additionally, the peak positions of these parameters, regardless of whether they are correct at the maximum angle, significantly depend on the rolling period, the rolling amplitude, and the gas flow rate. They might occur earlier in the cycle as the rolling period or amplitude increases or as the gas flow rate increases.