Multiple coexisting states of liquid rope coiling.

Ribe, N. M. and Huppert, H. E. and Hallworth, M. A. and Habibi, M. and Bonn, D. (2006) Multiple coexisting states of liquid rope coiling. Journal of Fluid Mechanics, 555. pp. 275-298. DOI

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A thin ‘rope’ of viscous fluid falling from a sufficient height onto a surface forms a series of regular coils. Here we investigate theoretically and experimentally a curious feature of this instability: the existence of multiple states with different frequencies at a fixed value of the fall height. Using a numerical model based on asymptotic ‘thin rope’ theory, we determine curves of coiling frequency Ω vs. fall height H as functions of the fluid viscosity ν, the diameter d of the injection hole, the volumetric injection rate Q, and the acceleration due to gravity g. In addition to the three coiling modes previously identified (viscous, gravitational and inertial), we find a new multivalued ‘inertio-gravitational’ mode that occurs at heights intermediate between gravitational and inertial coiling. In the limit when the rope is strongly stretched by gravity and Π1 ≡(ν5/gQ3)1/51, inertio-gravititational coiling occurs in the height range O(Π −1/6 1 )H(g/ν2)1/3 O(Π −5/48 1 ). The frequencies of the individual branches are proportional to (g/H)1/2, and agree closely with the eigenfrequencies of a whirling liquid string with negligible resistance to bending and twisting. The number of coexisting branches scales as Π5/32 1 . The predictions of the numerical model are in excellent agreement with laboratory experiments performed by two independent groups using different apparatus and working fluids. The experiments further show that interbranch transitions in the inertio-gravitational regime occur via an intermediate state with a ‘figure of eight’ geometry that changes the sense of rotation of the coiling.

Item Type: Article
Uncontrolled Keywords: 2006 AREP IA49 IA51 2006 P
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Journal of Fluid Mechanics
Volume: 555
Page Range: pp. 275-298
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:03
Last Modified: 23 Jul 2013 10:08

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