Investigation of flow characteristics and eddy viscosity ratio for air-oil intermittent flow in horizontal pipe

Experiments and three-dimensional numerical computations are performed to investigate the air-oil intermittent two-phase flow in a horizontal pipe for different air and oil flow rates. The numerical predictions of pressure drop and flow structure are compared with the experimental results to validate the numerical model. At a higher airflow rate, regardless of the oil flow rate, a mixing vortex formed by the velocity difference between the liquid film and liquid slug causes smaller bubbles to detach from the elongated bubble and disperse into the flow. The eddy viscosity ratio in the elongated bubble unit, which is challenging to measure by the experimental method, is numerically calculated to infer the mixing vortex and verify interfacial turbulence dampening in the air-oil intermittent flow regime. Due to surface tension, the eddy viscosity ratio is completely suppressed at the air-oil interface signifying the interfacial turbulence dampening in the air-oil intermittent flow regime.