Dynamics of liquid-liquid flows in horizontal pipes using simultaneous two-line planar laser-induced fluorescence and particle velocimetry

摘要

Experimental investigations are reported of stratified and stratified-wavy oil-water flows in horizontal pipes, based on the development and application of a novel simultaneous two-line (two-colour) technique combining planar laser-induced fluorescence with particle image/tracking velocimetry. This approach allows the study of fluid combinations with properties similar to those encountered in industrial field-applications in terms of density, viscosity, and interfacial tension, even though their refractive indices are not matched, and represents the first attempt to obtain detailed, spatiotemporally-resolved, full 2-D planar-field phase and velocity information in such flows. The flow conditions studied span mixture velocities in the range 0.3-0.6 m/s and low water-cuts up to 20%, corresponding to in situ (local) Reynolds numbers of 1750-3350 in the oil phase and 2860-11,650 in the water phase, and covering the laminar/transitional and transitional/turbulent flow regimes for the oil and water phases, respectively. Detailed, spatiotemporally-resolved in situ phase and velocity data in a vertical plane aligned with the pipe centreline and extending across the entire height of the channel through both phases are analysed to provide statistical information on the interface heights, mean axial and radial (vertical) velocity components, (rms) velocity fluctuations, Reynolds stresses, and mixing lengths. The mean liquid-liquid interface height is mainly determined by the flow water cut and is relatively insensitive (up to 20% the highest water cut) to changes in the mixture velocity, although as the mixture velocity increases the interfacial profile transitions gradually from being relatively flat to containing higher amplitude waves. The mean velocity profiles show characteristics of both laminar and turbulent flow, and interesting interactions between the two co-flowing phases. In general, mean axial velocity profiles in the water phase collapse to some extent for a give