student profile: Mr Jack B Khallahle


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Thesis work

Thesis title: The revalidation of flow parameters in stratified gas-liquid flow in horizontal pipes using CFD technique.

Supervisors: Steven ARMFIELD , Nicholas WILLIAMSON

Thesis abstract:

The gas-liquid mixtures transportation in a horizontal pipe as two-phase stratified flow is examined. The stratified flow occurs at relatively low gas-liquid flowrates resulting in complete gravity separation allowing liquid to flow along the bottom of the pipe and gas along the top forming a gas-liquid interface at the interface height is defined by liquid loading or height from pipe invert level. The knowledge of the mechanics of two-phase flow is extremely important in the correct design of the pipes to deliver the desired flowrates, particularly in long pipelines where pressure changes occur.

The design of these pipelines requires accurate parameters such as pressure drop, liquid holdup and shear stresses at the walls and the interface since both fluids are flowing in the same direction but not necessarily at the same velocities. Many empirical correlations have been developed in the last 60 years to evaluate these parameters using both experimental and analytical methods. In this investigation, the CFD method is used as an alternative to experimental method to revalidate empirical correlations that have been widely used in the prediction of flow parameters for two-phase stratified and wavy flow regimes in horizontal pipes.

The improvement on the gas wall shear stress estimation at the interface level is sought in this investigation in order that reliable average gas wall shear stress is obtained for the calculation of other flow parameters. This research employed CFD method to review and revalidate the experimental work of Kowalski (1987) in the gas wall shear measurement which had experienced a drop in value near the gas-liquid-wall interface level as reported by Newton and Behnia (1996, 1998) experimental works. The average gas wall shear stress calculated incorporating improved gas wall shear stress at the interface level is crucial to the calculation of interfacial shear stress and pressure drop at given liquid loading under the stratified flow regime and within the stability limits when delivering the desired flowrates for process purposes.

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