Retraction of a viscoplastic liquid sheet
Résumé
The retraction dynamics of viscoplastic liquid sheets have been investigated numerically by performing two-dimensional numerical simulations. The problem is mainly governed by two dimensionless numbers: the Ohnesorge number, Oh, which is the ratio between viscous and inertia-capillary forces, and, the plastic number, Pl, which represents the plastic nature of the fluid (related to the yield stress). Investigations are performed for a wide range of Oh (0.1–10), starting from a low Oh where the inertia-capillary force is dominant to a high Oh where the viscous effect is dominant. The effect of plasticity is investigated in each regime. Although the effect of plasticity on the retraction dynamics is less prominent at lower Oh, the effect is very significant at higher Oh. We demonstrate that in the case of a viscoplastic fluid, the retraction dynamics depends on the strain rate distribution within the liquid sheet. Using force balance, we determine the criteria for the retraction of the extended liquid sheet in terms of the Oh and Pl numbers.