On the role of droplets in cocurrent annular and churn-annular pipe flow |
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Authors: | J.M.C. van &rsquo t Westende,H.K. KempR.J. Belt,L.M. PortelaR.F. Mudde,R.V.A. Oliemans |
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Affiliation: | J.M. Burgerscentrum for Fluid Mechanics, Delft University of Technology, Kramers Laboratorium, Prins Bernhardlaan 6, 2628 BW Delft, The Netherlands |
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Abstract: | Decreasing the gas flow-rate in an initially vertical upward annular dispersed pipe-flow, will eventually lead to a down-flow of liquid. The onset of this down-flow has been related in the literature to the presence of the dispersed phase and the instability of the liquid film. Here we investigate how the dispersed-phase may influence the down-flow, performing detailed PDA-measurements in a 5 cm vertical air–water annular-flow. It is shown that the dispersed-phase does not cause the liquid down-flow, but that it delays the onset of liquid down-flow. In cocurrent annular flow the dispersed phase seems to stabilise the film flow, whereas in churn-annular flow the opposite seems to be true. |
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Keywords: | Upward annular flow Two-phase gas&ndash liquid flow Droplets PDA |
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