Transition between stratified and non-stratified horizontal oil-water flows. Part I

Stability analysis

Talal Al-Wahaibi, Panagiota Angeli

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

The characteristics of waves at the interface of oil-water stratified flow and at the onset of entrainment, where drops of one phase appear into the other, were studied. Theoretically a model was developed based on Kelvin-Helmholtz instability to predict the critical wave amplitude at which the waves become unstable for a specific wavelength. According to the model, waves become unstable in stratified flow when at a particular wavelength they exceed a critical amplitude, which decreases with increasing wavelength until it acquires an almost constant value. The model predictions showed that for low-viscosity oils the maximum critical amplitude appears at slip velocity close to zero, while for high-viscosity oils, the maximum amplitude appears for water velocity higher than that of the oil. Also the required entrainment wavelength over the pipe diameter, calculated using literature experimental onset conditions, was found to decrease as the viscosity of the oil increased. Experimentally, wave characteristics before and at the onset of entrainment were investigated by measuring the instantaneous fluctuations of the interface between oil (5.5 mPa s, 828 kg / m3) and water in a 0.038 m ID stainless steel horizontal pipe using a conductivity probe. The formation of drops and the onset of entrainment were identified using a high-speed video camera. At the onset of entrainment, wave characteristics were above the stability lines predicted by the model. Using a semi-empirical characteristic amplitude and wavelength in the model, it was possible to predict the onset of entrainment and transition from stratified to other mixed flow patterns reported in a number of studies.

Original languageEnglish
Pages (from-to)2915-2928
Number of pages14
JournalChemical Engineering Science
Volume62
Issue number11
DOIs
Publication statusPublished - Jun 2007

Fingerprint

Oils
Water
Wavelength
Viscosity
Pipe
High speed cameras
Stainless Steel
Video cameras
Flow patterns
Stainless steel

Keywords

  • Dual continuous flow
  • KH instability
  • Liquid-liquid flow
  • Onset of entrainment
  • Stratified flow
  • Wave characteristics

ASJC Scopus subject areas

  • Chemical Engineering(all)

Cite this

Transition between stratified and non-stratified horizontal oil-water flows. Part I : Stability analysis. / Al-Wahaibi, Talal; Angeli, Panagiota.

In: Chemical Engineering Science, Vol. 62, No. 11, 06.2007, p. 2915-2928.

Research output: Contribution to journalArticle

@article{f2208f38a9c04e1f925936fafc5ebcfc,
title = "Transition between stratified and non-stratified horizontal oil-water flows. Part I: Stability analysis",
abstract = "The characteristics of waves at the interface of oil-water stratified flow and at the onset of entrainment, where drops of one phase appear into the other, were studied. Theoretically a model was developed based on Kelvin-Helmholtz instability to predict the critical wave amplitude at which the waves become unstable for a specific wavelength. According to the model, waves become unstable in stratified flow when at a particular wavelength they exceed a critical amplitude, which decreases with increasing wavelength until it acquires an almost constant value. The model predictions showed that for low-viscosity oils the maximum critical amplitude appears at slip velocity close to zero, while for high-viscosity oils, the maximum amplitude appears for water velocity higher than that of the oil. Also the required entrainment wavelength over the pipe diameter, calculated using literature experimental onset conditions, was found to decrease as the viscosity of the oil increased. Experimentally, wave characteristics before and at the onset of entrainment were investigated by measuring the instantaneous fluctuations of the interface between oil (5.5 mPa s, 828 kg / m3) and water in a 0.038 m ID stainless steel horizontal pipe using a conductivity probe. The formation of drops and the onset of entrainment were identified using a high-speed video camera. At the onset of entrainment, wave characteristics were above the stability lines predicted by the model. Using a semi-empirical characteristic amplitude and wavelength in the model, it was possible to predict the onset of entrainment and transition from stratified to other mixed flow patterns reported in a number of studies.",
keywords = "Dual continuous flow, KH instability, Liquid-liquid flow, Onset of entrainment, Stratified flow, Wave characteristics",
author = "Talal Al-Wahaibi and Panagiota Angeli",
year = "2007",
month = "6",
doi = "10.1016/j.ces.2007.01.024",
language = "English",
volume = "62",
pages = "2915--2928",
journal = "Chemical Engineering Science",
issn = "0009-2509",
publisher = "Elsevier BV",
number = "11",

}

TY - JOUR

T1 - Transition between stratified and non-stratified horizontal oil-water flows. Part I

T2 - Stability analysis

AU - Al-Wahaibi, Talal

AU - Angeli, Panagiota

PY - 2007/6

Y1 - 2007/6

N2 - The characteristics of waves at the interface of oil-water stratified flow and at the onset of entrainment, where drops of one phase appear into the other, were studied. Theoretically a model was developed based on Kelvin-Helmholtz instability to predict the critical wave amplitude at which the waves become unstable for a specific wavelength. According to the model, waves become unstable in stratified flow when at a particular wavelength they exceed a critical amplitude, which decreases with increasing wavelength until it acquires an almost constant value. The model predictions showed that for low-viscosity oils the maximum critical amplitude appears at slip velocity close to zero, while for high-viscosity oils, the maximum amplitude appears for water velocity higher than that of the oil. Also the required entrainment wavelength over the pipe diameter, calculated using literature experimental onset conditions, was found to decrease as the viscosity of the oil increased. Experimentally, wave characteristics before and at the onset of entrainment were investigated by measuring the instantaneous fluctuations of the interface between oil (5.5 mPa s, 828 kg / m3) and water in a 0.038 m ID stainless steel horizontal pipe using a conductivity probe. The formation of drops and the onset of entrainment were identified using a high-speed video camera. At the onset of entrainment, wave characteristics were above the stability lines predicted by the model. Using a semi-empirical characteristic amplitude and wavelength in the model, it was possible to predict the onset of entrainment and transition from stratified to other mixed flow patterns reported in a number of studies.

AB - The characteristics of waves at the interface of oil-water stratified flow and at the onset of entrainment, where drops of one phase appear into the other, were studied. Theoretically a model was developed based on Kelvin-Helmholtz instability to predict the critical wave amplitude at which the waves become unstable for a specific wavelength. According to the model, waves become unstable in stratified flow when at a particular wavelength they exceed a critical amplitude, which decreases with increasing wavelength until it acquires an almost constant value. The model predictions showed that for low-viscosity oils the maximum critical amplitude appears at slip velocity close to zero, while for high-viscosity oils, the maximum amplitude appears for water velocity higher than that of the oil. Also the required entrainment wavelength over the pipe diameter, calculated using literature experimental onset conditions, was found to decrease as the viscosity of the oil increased. Experimentally, wave characteristics before and at the onset of entrainment were investigated by measuring the instantaneous fluctuations of the interface between oil (5.5 mPa s, 828 kg / m3) and water in a 0.038 m ID stainless steel horizontal pipe using a conductivity probe. The formation of drops and the onset of entrainment were identified using a high-speed video camera. At the onset of entrainment, wave characteristics were above the stability lines predicted by the model. Using a semi-empirical characteristic amplitude and wavelength in the model, it was possible to predict the onset of entrainment and transition from stratified to other mixed flow patterns reported in a number of studies.

KW - Dual continuous flow

KW - KH instability

KW - Liquid-liquid flow

KW - Onset of entrainment

KW - Stratified flow

KW - Wave characteristics

UR - http://www.scopus.com/inward/record.url?scp=34247520867&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34247520867&partnerID=8YFLogxK

U2 - 10.1016/j.ces.2007.01.024

DO - 10.1016/j.ces.2007.01.024

M3 - Article

VL - 62

SP - 2915

EP - 2928

JO - Chemical Engineering Science

JF - Chemical Engineering Science

SN - 0009-2509

IS - 11

ER -