Dynamic Models in Multiphase Flow

Transport of oil and gas mixtures in pipelines involves flow dynamics on a wide range of time and length scales. Liquid slugs and waves occur at scales extending from diameters ("hydrodynamic slug flow") and up to riser lengths ("severe slugging"). The approach in one-dimensional dynamic multiphase flow models for analysis of flow dynamics depends upon the scale to be resolved. Types of models are discussed, and a hybrid two-fluid model and a slug tracking model are in particular described. A two-fluid model is applied on a stationary grid in the gas-liquid stratified flow region until a slug is formed (or initiated), when a slug tracking method with a moving grid takes over. The performance of the model is demonstrated in relation to three types of cases with different time and length scales: Two- and three-phase severe slugging, hydrodynamic slugging after a bend, and a pigging case to simulate the rapid release of a hydrate plug. The computations are compared to experimental laboratory data.