Effect of Rolling Motion on Local Characteristics of Gas-liquid Two-phase Flow Using an Optical Probe

In order to get more local interfacial information as well as to further comprehend the intrinsic mechanism of two-phase flow under rolling condition to improve and extend the two-fluid model in rolling condition, an experimental investigation of two-phase flow under rolling as well as vertical steady condition was conducted by using double-sensor optical probe fabricated by the authors. The experimental loop is fixed on a rolling platform, which can simulate the rolling movement of a ship with the rolling period and rolling angle in the ranges of 0-20s and 30-45 degrees, respectively. An optical probe driven by a mechanical traverser is installed on the test section, wherein making it move diametrically. Experimental investigations were conducted on this experimental loop for air-water two-phase flow under rolling and steady conditions. Local void fraction, interfacial area concentration (IAC) and bubble velocity were obtained for further improving the interface transportation equation. Both the measured void fraction and IAC demonstrated wall peak or core peak distributions under vertical condition. The typical distribution of IAC under vertical conditions showed that IAC changes from wall peak to core peak with the gas flow rate increasing; while as the liquid flow rate increases, the distribution changes inversely. In the case of rolling conditions, despite similar to the distribution under vertical condition, the local time-averaged void fraction and LAC have lower value in centerline and high value near wall region. The results also indicated that the rolling amplitude has an influence on the local bubble frequency, void fraction and IAC, except interface velocity, while rolling period almost has no effect on the local characteristics.