A unified model to predict flow pattern transitions in horizontal and slightly inclined two-phase gas/shear-thinning fluid pipe flows. (September 2016) - Picchi, Davide
Highlights: We proposed a complete flow pattern map for gas/shear-thinning fluid pipe flows. We studied the non-linear stability analysis of the stratified flow. The rheology of the shear-thinning liquid affects the boundaries shape. We proposed and validated a two-fluid model for gas/shear-thinning annular flows. The transition boundaries were validated with experimental data. Abstract: Flow pattern transitions in two-phase gas/shear-thinning fluid pipe flows represent a key aspect during oil transportation and in chemical industry. In this paper a unified model to build a complete flow pattern map is proposed and models to predict flow patterns are provided. The transitions from stratified flow regime are investigates performing a linear stability and well-posedness analyses, and a non-linear stability analysis. The steady and fully developed two-fluid model for the annular flow is proposed and validated; the flow pattern transition from the annular flow is discussed considering, also, the structural stability. The transition to dispersed flow, the slug stability approach, and criteria to obtain the slug/plug and the bubbly/plug boundaries are considered. A sensitivity analysis on the effect of the rheology of the shear-thinning fluid on flow pattern boundaries is carried out and, then, the complete flow pattern maps are validated with data taken from the literature showing a good agreement.