Comments on “Drag Reduction Phenomenon in Viscous Oil-Water Dispersed
Pipe Flow…” regarding slip ratio
Abstract
In Rodriguez et al.1 an analytical expression was
deduced to predict the slip ratio in dispersed oil-water flow. Although
the quantitative agreement was quite good, the expression systematically
underestimated the slip ratio. New experimental data of similar flows
were collected in two different experimental facilities in pipes of
different materials and diameters (26 mm and 82.8 mm i.d.). Oil-water
flow data collected within a range of mixture Reynolds numbers from
1∙105 to 20∙106 in glass, acrylic and steel pipes with oil viscosities
varying from 7 to 220 mPa.s were used to deduce a more generic
correlation for slip ratio as a function of the mixture Froud number (5
< Fr < 70). The underestimation of the slip ratio
was corrected. The new slip-ratio correlation can be used to
significantly improve the prediction of volumetric fraction in flow
situations where turbulent dispersion of oil in water occurs.