Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.
Oil and gas from offshore reservoirs can flow as multiphase mixtures through well tubings, sub-sea flow lines and through risers to floating receiving facilities. Dynamic flow simulators are used to analyse the flow stability of such systems. Different model concepts are discussed and compared for the case of expansion driven flow instabilities. This is a class of flow instability where even a small amount of trapped gas upstream a riser base can cause oscillating flows due to expansion effects as the gas propagates along the riser. Some qualitative experiments have been made in a small scale setup to demonstrate the flow instabilities.