Numerical investigations of a swirling two-phase air-water upward flow in straight and convergent vertical pipe

Original Manuscript Submitted: 3/3/2023; Final Draft Received: 3/22/2023 In this study, a numerical study is presented to analyze the flow parameters such as longitudinal and transverse velocities, hydrodynamic pressure, and volume fraction inside a vertical pipe. A vertical ascending swirl flow is established with the specified boundary conditions and compared between straight and convergent geometry pipes. Normalized film thickness is found to vary between 0.4 and 0.6, where the numerical output data from the present study resemble wire-mesh sensor data from literature. Convergent pipe flow includes the variation of hydrodynamic pressure thereby affecting the slug and bubble flow region. Longitudinal and transverse velocities are plotted against time and compared at the three inspection planes near the inlet, mid-portion, and outlet, respectively. In order to understand the effectiveness of rotational effect of gas and liquid phases, the vorticity components are studied. Parameters such as Q-criterion and vortex stretching term indicate the straining and shearing flow near the peripheral and core regions. The temporal volume fraction variation at the output section indicates the increase in the output liquid yield of convergent pipe outlet by 17%.