Interface Investigation of Core-annular Flow

Master thesis (2018)

Authors

K. Jia Mechanical Engineering

Contributors

R.A.W.M. Henkes (supervisor 1)
Faculty
Mechanical Engineering
Copyright: © 2018 Kangjun Jia
CFD Core-annular flow Interface Capturing Coupled Level-Set Volume of Fluid Method
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Published Date

26-11-2018

Language

English

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Faculty

Mechanical Engineering

Abstract

The transport of highly-viscous oil in the core-annular flow regime in a horizontal pipe is investigated with a numerical simulation study. In this flow type the viscous oil is lubricated by a water annulus along the pipe wall. The Launder-Sharma low-Reynolds number k-ε turbulence model is used with the Volume-of-Fluid solver in interFOAM. Three types of simulations were carried out: 3D multiphase flow in a pipe section, 2D multiphase flow in an axi-symmetric pipe section (wedge-shaped section), in which gravity is ignored, and 2D single phase water flow in the annulus, using an imposed wavy boundary. This enabled to study the effect of the viscous oil core on the annulus behaviour, such as the turbulence structures and possible dispersion of oil into the water annulus. In particular the rationale of a 'solid-core' assumption is discussed through the comparison between simulations for the annulus that use the 'interface-bounded' flow and 'wall-bounded' flow.

A main finding of this study is that the use of the Compressive Volume of Fluid (CVOF) method in the multiphase simulations gives spurious dispersion of oil in the water annulus. This is the primary cause of the over-prediction of the pressure gradient simulations carried out in a previous study. Therefore, the Coupled Level-Set Volume of Fluid (CLSVOF) interface capturing method has been implemented in the 3D multiphase model. The new predictions show a good agreement with the experimental data at 20, 30, 40℃ (corresponding to a descrease in the oil viscosity). The oil dispersion in the annulus region close to the wall is diminished by using the new method while the sharpness of the interface is not improved. The CLSVOF interface capturing method is concluded to be an efficient and reliable interface capturing method for the numerical prediction of core-annular flow.