This thesis is aimed at developing a fundamental understanding of the key physical mechanisms associated with swirling gas-liquid flow in a vertical pipe, in order to construct a mechanistic model for predicting the flow behaviour. The model is based on quasi-1D reasoning, in analogy to the classical models for gas-liquid flow without swirl. As a benchmark case, it is used to investigate the onset of columnar flow patterns that are characteristic to swirling multiphase flow, for low gas input flows.

Experimental investigation of swirling vertical gas-liquid flow regimes. Different columnar flow patterns were observed and were used to construct flow regime maps. Four swirl elements were used to investigate the effect of swirl intensity on the flow regimes. An attempt was made to model the transitions between these columnar flow patterns.