Simulations for the interfacial waves in air-water annular flow in upward inclined tubes

Abstract

A numerical model is developed using the interIsoFoam solver within the OpenFOAM-v2106 framework to investigate gas-liquid two-phase annular flow in inclined tubes, with a specific focus on upward flow at five different inclination angles. The tube, which is 700 mm long with an inner diameter of 11.7 mm. The working fluid consists of air and water at atmospheric pressure, with the gas phase exhibiting a superficial velocity of 18 m/s, and the liquid film characterized by a liquid film Reynolds number (Re_f) of 350. Near the inlet, high-frequency, low-amplitude initial waves are present. As the flow develops, these waves evolve into slower ripples at the top of the tube, particularly in the horizontal tube. Meanwhile, at the bottom, they transition into high-amplitude disturbance waves. This progression reflects the distinct evolution of wave types at the top and bottom as the flow progresses. The base liquid film thickness and interfacial wave amplitude in the inclined tube exhibit pronounced circumferential non-uniformity, with both decreasing gradually from the top to the bottom. This non-uniformity becomes more pronounced as the inclination angle decreases. An edge detection algorithm is used to identify the characteristic lines of ripple and disturbance waves, aiding in the investigation of circumferential wave velocity variations within the tube.