Age dependence of the drag force in an aqueous foam |
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Authors: | John R de Bruyn |
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Institution: | (1) Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada, N6A 3K7;(2) Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada, A1B 3X7;(3) Laboratoire de Rhéologie, B.P. 53, Domaine Universitaire, Grenoble, 38041, Cedex 9, France |
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Abstract: | The drag force on a sphere moving through an aqueous foam is measured as the foam ages. After an initial period, the steady-state drag decreases with age T as T
−0.54±0.14. As the mean bubble size R in the foam coarsens as T
0.5, this implies that the drag force scales as The transient buildup of the force when the sphere starts to move is described by a single exponential approach to the steady-state drag while its relaxation when the motion stops is described by the sum of three exponential relaxations. This is as for fresh foam, but the coefficients and time constants vary systematically with age. For the most part, these quantities also show a power law scaling with T. The age dependence of the quantities determined in this study is discussed in terms of the mean bubble size. |
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Keywords: | Foam rheology Drag force Coarsening Yield stress Stress relaxation |
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