Abstract
In this paper the effect of a transverse cylindrical rod immersed in water on the flow patterns and interfacial characteristics of an oil–water pipe flow is investigated experimentally. The cylinder is used to passively actuate the transition from stratified to non-stratified flows and to localise the formation of waves and the detachment of drops. The studies are carried out in an acrylic test section with 37mm ID using as test fluids tap water and Exxsol D140 (density 830kgm−3 and viscosity 5.5cP). The rod has 5mm diameter and is located at 460mm from the test section inlet. Flow patterns and interface characteristics were studied with high speed imaging. It was found that the presence of the rod generates waves shortly downstream, from which drops detach, and reduces the mixture velocity for the transition from stratified to non-stratified flows. The average interface height and wave amplitude increase with distance from the rod, while the average wave length and frequency remain almost constant. The Strouhal number is found to be equal to 0.24, while the wave velocities are slightly higher than the mixture velocities.
Highlights
The simultaneous flow of two immiscible liquids inside a pipe is commonly encountered in many applications including transportation in the petroleum industry, emulsifications and twophase reactions and separations in the process industries
Flow patterns were observed in both cases without and with the bluff body with the high speed camera at 7 m downstream the inlet (189D)
In this paper the effect of a cylindrical bluff body placed inside a pipe to the flow patterns and interface characteristics of a twophase liquid–liquid system were studied experimentally, using high speed imaging and a conductance probe
Summary
The simultaneous flow of two immiscible liquids inside a pipe is commonly encountered in many applications including transportation in the petroleum industry, emulsifications and twophase reactions and separations in the process industries. The results were later confirmed by Barral et al [18] who used a conductance probe and high speed imaging to obtain interfacial wave characteristics In both studies, the exact axial location in the pipe where drops detach and the transition from stratified to non-stratified flows was not identified. Lin and Rockwell [30] studied the free surface shape and breaking waves downstream a hydrofoil and obtained velocity profiles using Particle Image Velocimetry (PIV) They observed a sharp elevation of the interface just behind the blufpf bffiffiffioffiffidy which increased with increasing Froude number (Fr 1⁄4 u= gd, where g, d and u are the gravitational force, foil chord length and free stream velocity respectively). The current work investigates the effect of a cylinder immersed in the water phase of a twophase oil–water pipe flow on the interface characteristics, using high speed imaging and conductance probes. For the first time the combined interactions of a bluff body with a wall and an interface are considered
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