General model for transient homogeneous gas–liquid pipe flows with non-uniform gas convection

Accurate modelling of transient homogeneous gas–liquid flow is crucial for the design and operation of various pipe systems. Although the classical model is simple and efficient under low gas volume fraction conditions, it relies on the uniform gas convection assumption and ignores temporal gas mass variations within each control volume. This usually produces significant modelling errors under real-world non-uniform gas distributions. To address this problem, this paper formulates a general model that relaxes the uniform gas convection assumption, which is solved numerically using an exact Riemann solver. The proposed model and scheme are rigorously validated against numerical, experimental, and analytical data for scenarios of varying complexity. Moreover, numerical experiments demonstrate that the general model successfully resolves the spatial and temporal evolution of non-uniform gas convection, overcoming a key deficiency of the classical model. Key Points: A general model for transient homogeneous gas–liquid pipe flows is formulated considering the non-uniform gas convection. The general model is systematically validated against numerical, experimental, and analytical data for scenarios of varying complexity. Unlike the classical model, the general model accurately captures the non-uniform gas phase convection along the pipe.