Experimental investigations of upward-inclined stratified oil-water flows using simultaneous two-line planar laser-induced fluorescence and particle velocimetry. (February 2021)

• Record Type: Journal Article
• Authors: Ibarra, Roberto; Matar, Omar K.; Markides, Christos N.
• Is Part Of: International journal of multiphase flow. Volume 135(2021)
• Publication Date: 2021-02
• Subjects: Flow structures -- Inclined flows -- Laser-induced fluorescence -- Liquid-liquid flows -- Oil-water pipe flow -- Particle image velocimetry; Multiphase flow -- Periodicals; Écoulement polyphasique -- Périodiques; Multiphase flow; Periodicals; 620.1064
• DOI: 10.1016/j.ijmultiphaseflow.2020.103502
• Languages: English
• ISSNs: 0301-9322

Abstract

Highlights: Two-line PLIF-PIV in inclined (≤5°) upward stratified, low-water-cut (10-20%) oil-water flows. Complex flow structures are revealed as contributing to unsteadiness and wave generation. Statistics on interface height, mean/rms velocity profiles and Reynolds stresses reported. Velocity characteristics are dependent on the pipe inclination and inlet flow conditions. Predictions from a linear mixing-length model agree reasonably well with measurements. Abstract: Experiments are performed in low-inclination (≤ 5°) upward stratified oil (Exxsol D140) and water flows. The flows are investigated using a novel two-line laser-based diagnostic measurement technique that combines planar laser-induced fluorescence and particle image/tracking velocimetry to obtain two-dimensional (2-D) space- and time-resolved phase and velocity information. The technique enables direct measurements in the non-refractive-index-matched fluids of interest, as opposed to substitute fluids which are matched optically but whose properties may be less representative of those in real field applications. Flow conditions span in situ Reynolds numbers in the range 1300-3630 in the oil phase and 1810-11540 in the water phase, and water cuts of 10% and 20%. Instantaneous velocity vector-fields reveal the presence of complex flow structures in the water phase at low mixture velocities, which become less coherent with increasing pipe inclinations. These structures contribute to the generation of interfacial waves, increase the unsteadiness of the flow and the rate of momentum transfer to the oil phase. Statistical information on the interface heights, mean axial and wall-normal velocity profiles and fluctuations, Reynolds stresses, and mixing lengths is obtained from the analysis of the spatiotemporally resolved phase and velocity data. The normalised mean and rms velocity characteristics (velocity fluctuations and Reynolds stress) are shown to be weakly-dependent on the pipe inclination as the mixture velocity increases. Finally, predictions from a linear mixing-length model agree reasonably well with measurements for the water layer and near-interface regions.