CFD modelling of stratified two-phase flow for oil and gas transportation

Stratified two-phase flow is a flow regime typically encountered in gas transportation pipelines, where a small amount of hydrocarbon condensate, and in multiphase pipelines. For safe and optimal operation of the pipeline , it is crucial to carry out accurate prediction of the main characteristic of the flow (e.g. pressure gradient, hold up , flow regimes, turbulent quantities, thermal effects) . Nowadays the software used to simulate pipelines system are based on one dimensional models, in which the local instantaneous momentum balances are averaged over the cross section of the pipe. Although such models are the only practical solution to solve long pipeline system, they present some issues. In fact the information over the cross section are lost, thus these models present inaccuracies when three-dimensional effects are important or when a detailed description of the turbulent quantities is necessary. In these cases CFD become an interesting tool , since it can be employed in that sections of the pipe where a detailed solution of the flow is necessary. However, the classical turbulence models do not correctly represent the turbulence behavior of the interface. In this thesis a RANS code has been developed through Matlab to simulate steady state, fully developed stratified two-phase flow between two flat plates. The code has been used to develop and test a modify version of the k- ω model, where a damping of the turbulence is imposed at the interface. The results were compared with the experiment of Fabre et al. (1987) and Akai et al. (1981)