The prediction of three-phase gas-liquid-liquid flows is of central importance to the oil industry. Bearing in mind that even two-phase gas-liquid flows are highly complex, it is immediately apparent that the addition of a third phase will add to this complexity. A key issue is the interaction of the two liquid phases. If these phases are well mixed, then the influence of the anomalous viscosity at the point of phase inversion can become very great giving rise to peaks in void fraction and liquid hold-up. This paper describes the outcome of a joint study at Imperial College in which both numerical and experimental investigations of three-phase slug flow were conducted. The experimental work was carried out on the Imperial College WASP facility. Measurements were made of the characteristics of the flows, and in particular the time -varying and time-averaged hold-up of the phases and pressure gradients using a scanning dual energy gamma densitometer. In the parallel computational study, predictions were made of the slug flow characteristics using a modified two-fluid model. This model incorporated the influence of the additional liquid phase by using a "drift-flux" approach and mixing processes were represented by a model developed by Decarre & Fabre (11). The local liquid viscosity was calculated using the model of Brinkman. Despite the complexity of three-phase slug flow, the model was remarkably effective in predicting the measured flow characteristics and could form a basis for improved predictions of three-phase flows in future.
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