A Computational Study of the Influence of Viscoelasticity On the Interfacial Dynamics of Dip Coating Flows

We examine the effect of viscoelasticity on the interfacial dynamics of air displacing a viscoelastic fluid under the presence of gravity, i.e., the dip coating flow. A stabilized finite element method coupled with a pseudo-solid domain mapping technique is used for completing the computations. The fluid is modeled by the Finitely Extensible Non-linear Elastic-Peterlin (FENE-P) constitutive equation. For all values of Capillary number, Ca and Bond number, Bo the flow is characterized by recirculation near the interface. Increasing Bo, at a fixed Ca, results in film thinning and an increase in the strain rates near the interface. We also observe that the film thickness, as a function of the Weissenberg number Wi, scaled with the capillary length at low Ca and high Bo collapses onto a single curve. As the value of Ca is increased, again the film thickness scaled with the capillary length collapses onto a single curve, but at increasingly higher values of Bo. We show that the interfacial dynamics in the dip coating flow are qualitatively similar to those observed in the Hele-Shaw type of flow. At low Wi, there is film thinning and as the value of Wi is increased, we observe the formation of normal elastic stress boundary layers in the capillary transition region. This is accompanied by a sharp increase in the film thickness and a compression of the bubble in the capillary transition region.