Liquid Inlet Boundary Effect on the Simulation of Liquid Waves in Vertical Air-Water Churn Flow

The present study investigates the influence of liquid inlet modelling on the development of liquid waves in isothermal churn flow of air and water in a vertical pipe. The porous wall liquid inlet section, commonly used in experiments, is modelled as a simple inlet flow area in our simulation. Using the liquid mass flow rate from experiment, the magnitude of the wall normal velocity component is determined by the inlet area which is used as a modelling parameter. This parameter significantly affects the calculated liquid wave frequency. The inlet liquid velocity profile was not measured in available experiments and thus presents a major source of uncertainty in simulations. The parametric analysis shows that a suitable liquid inlet area can be determined over the range of liquid flow rates, leading to good agreement of simulated and measured wave frequencies. A three-dimensional simulation was performed using the multiphase solver interFoam from the open-source code OpenFOAM.