This paper reports an effort to investigate the effect of flow velocities and inlet configurations on horizontal oil-water flows in a 32 mm ID acrylic pipe using water and an aliphatic oil (Exxsol D140) as test fluids. The flows of interest were analysed using pressure drop measurements and high-speed photography in an effort to obtain a flow pattern map, pressure gradient profiles and measures of the in situ phase fractions. The experiments reveal a particular effect of the inlet configuration on the observed flow patterns. A horizontal plate, installed at the inlet, generates a transition to stratified flow when the plate height closely matched the in situ water height at low water cuts.
The flow of oil and water in pipes is commonly encountered in a number of industrial processes. These systems are particularly relevant to the oil industry in which achieving a fundamental understanding of the oil-water flow behaviour is central to oil production, transportation, and equipment design. Moreover, the study of oil-water flows provides a stepping-stone towards developing an understanding of three-phase flows (e.g. oil-watergas flows). Oil-water flows have been studied extensively by several researchers (see, for example, Russell et al. ; Charles et al. ; Arirachakaran et al. ; Trallero ; Angeli and Hewitt , and references therein) whose main purpose was to characterise the resulting flow patterns, pressure gradients, in situ phase fractions and interfacial phenomena over a wide range of flow conditions, fluid properties and pipe configurations. However, the behaviour of these flows is still not well understood due to the complex phenomena encountered in pipeline systems, which extend beyond those in gas-liquid flows where the densities and viscosities of the two fluids are highly separated. Additional parameters, such as interfacial forces, wetting characteristics, and phase inversion, represent important factors due to the effect on the flow pattern transitions, interface curvature and droplet formation.
A number of complex geometrical configurations are encountered in oil-water flows for a given pipe material, inlet design, pipe inclination, fluid properties and flow velocities. The resulting flow patterns range from separated flows (e.g. stratified smooth, stratified wavy and stratified with droplets at the interface) to fully dispersed flows (e.g. dispersion of oil in water). For an intermediate range of velocities, dual continuous flows can be observed (Lovick and Angeli ).