Stability analysis of core‐annular flow and neutral stability wave number

Abstract

in Wiley InterScience (www.interscience.wiley.com).A general transition criterion is proposed in order to locate the core-annular flow pattern in horizontal and vertical oil-water flows. It is based on a rigorous one-dimensional two-fluid model of liquid-liquid two-phase flow and considers the existence of critical interfacial wave numbers related to a non-negligible interfacial tension term to which the linear stability theory still applies. The viscous laminar-laminar flow problem is fully resolved and turbulence effects on the stability are analyzed through experimentally obtained shape factors. The proposed general transition criterion includes in its formulation the inviscid Kelvin-Helmholtz's discriminator. If a theoretical maximum wavelength is considered as a necessary condition for stability, a stability criterion in terms of the Eo¨tvo¨s number is achieved. Effects of interfacial tension, viscosity ratio, density difference, and shape factors on the stability of core-annular flow are analyzed in detail. The more complete modeling allowed for the analysis of the neutral-stability wave number and the results strongly suggest that the interfacial tension term plays an indispensable role in the correct prediction of the stable region of core-annular flow pattern. The incorporation of a theoretical minimum wavelength into the transition model produced significantly better results. The criterion predictions were compared with recent data from the literature and the agreement is encouraging.

Pressure loss in core-annular flow: Modeling, experimental investigation and full-scale experiments

“…One can see in Fig. 5 that for the case studied in this work the predictions of the standard two-fluid model (Rodriguez and Bannwart, 2008) and those of Eq. (17) can be quite different (discrepancies as high as 25% are observed at high mixture velocities).…”

“…5. Frictional pressure drop as a function of oil superficial velocity for two fixed water superficial velocities (J 2 = 0.1 m/s and 1 m/s); dashed curves indicate predictions of the standard two-fluid model (Rodriguez and Bannwart, 2008) and solid curves indicate predictions of Eq. (17).…”

Characterization of liquid‐liquid flows in horizontal pipes

“…However, it is possible that the oil fouling accumulates overtime and even blocks the pipe, especially when the wax content in the oil is high and the adhered oil with wax builds up into hard structures. The mechanism of the stabilization of core‐annular flow in a horizontal pipe is still an open question and discussions can be found in Ooms et al, Bannwart, Rodriguez and Bannwart, and Beerens et al…”

“…In the petroleum industry, oil and water are frequently transported together in wells and pipelines. A lot of studies on particular liquid‐liquid flow systems, e.g., low‐viscosity oil‐water flow, high‐viscosity oil‐water flow, specific flow regimes such as stratified flow, dispersed flow and core annular flow, have been reported in the literature. These studies greatly contribute to our understanding of liquid‐liquid flows.…”

Modality transition-based network from multivariate time series for characterizing horizontal oil–water flow patterns

“…The characterization of oil-water°ows has attracted much attention from physical and chemical research¯elds. The wavelet multiresolution technique, 1 fractal analysis, 2,3 theoretical model, 4 particle image velocimetry technique 5 and measurement techniques such as capacitance probes, 6 nonintrusive optical probe, 7 wire-mesh sensor 8 and laser-induced°uorescence 9 have been employed to investigate two-phase°ow. But compared to the study of gas-liquid°ows, [10][11][12] works particularly dedicated to the research of horizontal oil-water°o ws are quite limited.…”