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Buoyancy driven flow of a viscous drop in viscoelastic materials

2023; Elsevier BV; Volume: 321; Linguagem: Inglês

10.1016/j.jnnfm.2023.105124

1873-2631

Giancarlo Esposito, Yannis Dimakopoulos, John Tsamopoulos,

Fluid Dynamics and Thin Films

We study the motion of a viscous drop rising in a viscoelastic liquid that exhibits elastic and shear thinning effects and is represented by the exponential PTT constitutive model. We validate the numerical formulation and solution method by comparing our predictions with previous experimental data, and we find quantitative agreement in terminal velocities and drop shapes. The interplay of viscous, elastic, and capillary forces is examined through an extensive parametric study. Increasing material elasticity of the continuous phase turns a spherical drop to one with a cusp and eventually with an extended tail in its rear pole. The viscoelastic extensional stresses developing in the continuous phase are crucial for the generation of these long tails. Low values of the interfacial tension allow the extension of threads of uniform width, but higher values break it under a Rayleigh-type instability. Increasing shear thinning increases the terminal velocity of the deformable intrusion. An important conclusion of this study is the confirmation that viscoelastic materials can be used to encapsulate small drops generated by the tip streaming of liquid filaments.