Drag reduction phenomenon in viscous oil-water dispersed pipe flow: experimental investigation and phenomenological modeling

Abstract

An experimental study on drag‐reduction phenomenon in dispersed oil‐water flow has been performed in a 26‐mm‐i.d. Twelve meter long horizontal glass pipe. The flow was characterized using a novel wire‐mesh sensor based on capacitance measurements and high‐speed video recording. New two‐phase pressure gradient, volume fraction, and phase distribution data have been used in the analysis. Drag reduction and slip ratio were detected at oil volume fractions between 10 and 45% and high mixture Reynolds numbers, and with water as the dominant phase. Phase‐fraction distribution diagrams and cross‐sectional imaging of the flow suggested the presence of a higher amount of water near to the pipe wall. Based on that, a phenomenology for explaining drag reduction in dispersed flow in a flow situation where slip ratio is significant is proposed. A simple phenomenological model is developed and the agreement between model predictions and data, including data from the literature, is encouraging.