Flow Characteristics and Control of Vertical Upward Gas-Liquid Two-Phase Flow through a Sudden Contraction Pipe

The effects of bubble size on an upward gas-liquid (CO 2-water) flow in a vertical pipe after an abrupt expansion is investigated visually and experimentally in the present work. The mean bubble size varies from small scale (d b =0.3mm) to relatively large scale (d b =4.5mm). Extensive visualization experiments and PIV analysis show different flow patterns downstream of the expansion of flows containing bubbles of different sizes. The effect of bubble size is also investigated measuring the pressure distribution along the pipe and the drag of the expansion and its difference under different bubble sizes is calculated and compared with that of single-phase flow. The fluctuation phenomena occurring downstream are also investigated. The experiments are conducted under constant Reynolds number (Re=1.0×10 4) and volumetric gas flow rate ratio (α v =0~10%). The present work gives valuable information about how the bubble size affects the flow characteristics even under steady flow conditions, and explains the differences between results reported by other authors investigating under similar conditions.

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Fluctuating Phenomena and Flow Control of Bubbly Two-Phase Flow Through Sudden Expansion Pipe

Voutsinas

Shakouchi

Tsujimoto

et al. 2009

JFST

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The fluctuating flow phenomena on a two-phase flow through a vertical sudden expansion pipe system are investigated experimentally and visually. The effect of the volumetric gas flow rate ratio within the range of bubbly flow is investigated. Simple flow control methods are proposed and tested in comparison with the normal expansion case. The first method applies control by mounting a ring shaped obstacle downstream the expansion, and the second by mounting a step-ring just downstream. These two methods are based on a different control concept. The first is based on splitting the vortex region, thus decreasing its intensity, and the second on decreasing the overall generated vortex region length. In single-phase flow, only one dominant frequency is observed. However, when gas is induced, two dominant peaks appear and a tendency of the second peak to shift to lower frequency values when increasing the volumetric gas fraction is observed. When the flow control methods are applied, the fluctuation frequency is not affected, but the fluctuation amplitude decreases. From pressure distribution measurements under several flow conditions, it was confirmed that when the flow control methods are applied, drag reduction is achieved as well.

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Flow Characteristics and Control of Vertical Upward Gas-Liquid Two-Phase Flow through a Sudden Contraction Pipe

Cited by 3 publications

References 7 publications

Behaviour of a large bubble flowing through a sudden constriction between a cylindrical pipe and a rectangular cross section channel

Behaviour of a large bubble flowing through a sudden constriction between a cylindrical pipe and a rectangular cross section channel

Investigation of Bubble Size Effect on Vertical Upward Bubbly Two-Phase Pipe Flow Consisted With an Abrupt Expansion

Fluctuating Phenomena and Flow Control of Bubbly Two-Phase Flow Through Sudden Expansion Pipe

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