Non-Axisymmetric Instability of Core-Annular Flow

Stability of core-annular flow of water and oil in a vertical circular pipe is studied with respect to nonaxisymmetric disturbances. Results show that when the oil core is thin, the flow is most unstable to the asymmetric sinuous mode of disturbance, and the core moves in the form of corkscrew waves as observed in experiments. The asymmetric mode of disturbance is the most dangerous mode for quite a wide range of material and flow parameters. This asymmetric mode persists in vertical pipes with upward and downward flows and in horizontal pipes. The analysis also applies to the instability of freely rising axisymmetric cigarette smoke or a thermal plume. The study predicts a unique wavelength for the asymmetric meandering waves. Disciplines Engineering | Mechanical Engineering Comments Suggested Citation: Hu, Howard H. and Neelesh Patankar. (1995) Non-axisymmetric instability of core-annular flow. Journal of Fluid Mechanics. Vol 290. p. 213-224. Copyright 1995 Cambridge University Press. http://dx.doi.org/10.1017/S0022112095002485 This journal article is available at ScholarlyCommons: http://repository.upenn.edu/meam_papers/212 J. Fluid Mech. (1999, vol. 290, p p . 21S224 Copyright