We study the transportation of highly viscous furnace-oil in a horizontal pipe as core-annular flow (CAF) using experiments. Pressure drop and high-speed images of the fully developed CAF are recorded for a wide range of flow rate combinations. The height profiles (with respect to the centerline of the pipe) of the upper and lower interfaces of the core are obtained using a high-speed camera and image analysis. Time series of the interface height are used to calculate the average holdup of the oil phase, speed of the interface, and the power spectra of the interface profile. We find that the ratio of the effective velocity of the annular fluid to the core velocity, , shows a large scatter. Using the average value of this ratio () yields a good estimate of the measured holdup for the whole range of flow rate ratios, mainly due to the low sensitivity of the holdup ratio to the velocity ratio. Dimensional analysis implies that, if the thickness of the annular fluid is much smaller than the pipe radius, then, for the given range of parameters in our experiments, the non-dimensional interface shape, as well as the non-dimensional wall shear stress, can depend only on the shear Reynolds number and the velocity ratio. Our experimental data show that, for both lower and upper interfaces, the normalized power spectrum of the interface height has a strong dependence on the shear Reynolds number. Specifically, for low shear Reynolds numbers, interfacial modes with large wavelengths dominate, while, for large shear Reynolds numbers, interfacial modes with small wavelengths dominate. Normalized variance of the interface height is higher at lower shear Reynolds numbers and tends to a constant with increasing shear Reynolds number. Surprisingly, our experimental data also show that the effective wall shear stress is, to a large extent, proportional to the square of the core velocity. Using the implied scalings for the holdup ratio and wall shear stress, we can derive an expression for the pressure drop across the pipe in terms of the flow rates, which agrees well with our experimental measurements.
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August 2017
Research Article|
August 18 2017
Characterization of interfacial waves and pressure drop in horizontal oil-water core-annular flows
Sumit Tripathi;
Sumit Tripathi
1
IITB-Monash Research Academy
, Mumbai 400076, India
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Rico F. Tabor;
Rico F. Tabor
2
School of Chemistry, Monash University
, Clayton 3800, Australia
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Ramesh Singh;
Ramesh Singh
3
Department of Mechanical Engineering, I.I.T. Bombay
, Mumbai 400076, India
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Amitabh Bhattacharya
Amitabh Bhattacharya
a)
3
Department of Mechanical Engineering, I.I.T. Bombay
, Mumbai 400076, India
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Sumit Tripathi
1
Rico F. Tabor
2
Ramesh Singh
3
Amitabh Bhattacharya
3,a)
1
IITB-Monash Research Academy
, Mumbai 400076, India
2
School of Chemistry, Monash University
, Clayton 3800, Australia
3
Department of Mechanical Engineering, I.I.T. Bombay
, Mumbai 400076, India
a)
Author to whom correspondence should be addressed: [email protected]
Physics of Fluids 29, 082109 (2017)
Article history
Received:
May 23 2017
Accepted:
July 29 2017
Citation
Sumit Tripathi, Rico F. Tabor, Ramesh Singh, Amitabh Bhattacharya; Characterization of interfacial waves and pressure drop in horizontal oil-water core-annular flows. Physics of Fluids 1 August 2017; 29 (8): 082109. https://doi.org/10.1063/1.4998428
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