Abstract
This paper investigates flow patterns encountered in two-phase swirling flow in a vertical pipe. Flows in the pipe are observed by using a high-speed video camera and the void fractions are calculated from the video images. Flows at various gas and liquid volumetric fluxes, JG and JL, are tested, i.e., 0.01 ≤ JG ≤ 8 m/s and 0.10 ≤ JL ≤ 0.80 m/s. When JL is higher than a certain value, no bubbles exist in a swirling flow but a gas column forms due to the centrifugal force even at low JG. The diameter of a gas column increases with JG at a constant JL. A tornado-shaped gas column forms at intermediate JG. At high JG, a liquid film including small bubbles and intermittent liquid slugs with many bubbles are observed. These flows are classified into four flow patterns based on the observations and the characteristics of void fraction. The statistical quantities of void fraction, i.e., the mean, standard deviation, skewness and kurtosis, are also computed. The validity of the flow pattern classification based on the statistical quantities has been confirmed.
