© 2001 by Oxford University Press
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Oscillatory Behaviour in Statically Stressed Viscoelastic Inflation Flow
( 1 Department of Mechanical and Materials Engineering, Faculty of Engineering Science, The University of Western Ontario, London, Ontario, Canada N6A 5B9 )
The influence of fluid elasticity is investigated by examining the biaxial inflation of a spherical shell of a viscoelastic fluid subject to a constant and a linearly ramped change of pressure. In contrast to the monotonic growth of a Newtonian fluid, that of a viscoelastic fluid is found to be oscillatory under conditions of large Deborah number, for a thick shell, and for sudden inception. Although this type of non-monotonic behaviour has been predicted in other similar flow configurations of viscoelastic fluids, there is no evidence of it occurring experimentally. The current calculations, in the case of a bubble growing in an infinite viscoelastic medium, show that, if a ramped rather than a sudden pressure is applied initially, the amplitude of the oscillations decreases as the rate of pressure decreases. This may explain why oscillations have not been observed in experiment, since a sudden initial driving pressure is difficult to realize.