A flow pattern map for two-phase liquid-gas flows under reduced gravity conditions

Two-phase gas-liquid flows have a wide range of applications in space including the flow of cryogenics in transport lines and heat-transfer fluids in a thermal control system. The behavior of these systems under reduced gravity must be understood in order to optimize the design and maintenance of such systems. Experimental studies on two-phase flow patterns and their transitions were conducted aboard the NASA KC-135 aircraft. A large set of flow pattern data for water-air and glycerin/water-air of different viscosities was reported. It was shown that two-phase flow under reduced gravity can be classified into four flow patterns: bubbly, slug, frothy slug-annular, and annular flows. Transitions between slug and frothy slug-annular, and frothy slug-annular and annular flows were predicted well using the liquid and gas Weber numbers as the mapping coordinates.