Calculating Column Separation in Liquid Pipelines Using a 1D-CFD Coupled Model

This paper proposes a coupled 1D-CFD model for calculating column separation in liquid pipelines. ANSYS Fluent is utilized to calculate two-phase flow analysis. Method of Characteristics and Discrete Gas Cavity Model (DGCM) are both employed to conduct 1D transient analysis. The results show that the proposed model, with both 2D and 3D CFD analysis, captures the transient responses of the system that have nearly identical accuracy and are both consistent with the results of a physical experiment. The results of a pure CFD analysis are employed to evaluate the performance of the proposed model in capturing the shape of the vapor cavity. The comparison shows that the results are generally consistent. However, the vapor cavity in the pure CFD model is established and grown on top of a film of liquid, while the cavity in some places fills the whole pipe cross-section in the proposed model. In addition, the results obtained from using Modified Two-Component Pressure Approach (MTPA), an open-channel based model proposed by the authors, also confirm the results obtained from the pure CFD analysis. Some minor discrepancies are found, which may be attributed to the uniform velocity distribution considered at the interface between 1D and CFD zones.