A unit cell model for gas-liquid pseudo-slug flow in pipes

Pseudo-slug flow is a subset of intermittent flow which has not been properly understood and modeled. However, this flow pattern is widely encountered in oil and gas production and transportation, driving the needs for proper modeling efforts. A new pseudo-slug unit cell model is proposed in this paper. The proposed model modifies the existing slug unit cell model by accounting the continuous gas passage, slippage, and interfacial momentum exchange in the pseudo-slug body. Pseudo-slug characteristics (length, velocity, and body holdup) reported in literature are incorporated through ad-hoc closure relationships. These closures remain to be improved in the future. Overall, the proposed model produces more accurate pressure gradient and film holdup (H-LF) predictions compared to two state-of-the-art models which generally treat pseudo-slug as slug flow (TUFFP Unified model and OLGAS 7.3.5 (R)).