Rigid and deformable particle interactions with viscoelastic fluid and solid materials
Open Access DepositedIn this work, the dynamics of single, double, and multiple deformable particles suspended in viscous and viscoelastic fluid have been numerically investigated with a front-tracking finite difference method. The mechanism of drop deformation, migration, coalescence, and aggregation plays a vital role in forming the macroscopic properties of emulsion. First, we study the dynamics of a viscoelastic drop suspended in a viscous fluid in a time-period rotating extensional flow (REF) at finite inertia. We investigate the effects of viscoelasticity on drop breakup in a potential vortex, which is a special case of rotating extensional flow. Viscoelasticity inhibits drop breakup, raising the critical capillary number, an effect more pronounced at lower inertia. We then study the pair-interactions between viscous drops suspended in a viscoelastic shear flow, examining the effects of elasticity and drop deformability on their post-collision trajectory. Two different trajectory types are identified depending on the Weissenberg number (Wi) and capillary number (Ca). Drops suspended in a Newtonian matrix (Wi=0.0) show a passing trajectory where drops slide past each other and separate in the streamwise direction. However, increasing the Weissenberg number above a critical value, a tumbling/doublet trajectory is observed where two drops rotate around the midpoint of the line joining their centers. The tumbling trajectory is explained by investigating the flow around a single drop in shear. Treating the tension along the curved streamlines due to the non-zero first normal stress difference in the viscoelastic medium as an enhancement to the interfacial tension, we have developed an approximate force balance model that qualitatively captures the observed scaling of the critical Ca and Wi values at the phase boundary. We extend our numerical simulation to the concentrated emulsion to study the effect of surrounding fluid viscoelasticity on the shear-induced diffusion of drops. A compact layer of viscous drops in a viscous shear flow diffuses along the velocity gradient direction because of irreversible pair-particle interactions. However, in a viscoelastic shear flow, drop diffusion reduces monotonically. We vary drop deformability and surrounding fluid viscoelasticity to understand the effect of fluid viscoelasticity on collective diffusivity. At lower Capillary (Ca) and higher Weissenberg (Wi) numbers, the drop diffusion is completely hindered by fluid viscoelasticity, and zero diffusion is observed. Finally, the capability of the existing parallel front tracking code has been extended by implementing rigid boundary and viscoelastic solid models that allow us to simulate flow in complex rigid boundaries and resolve associated fluid-solid interaction. Using this new capability, we investigate the force acting on a spherical rigid body indenting on a viscoelastic solid submerged in a fluid environment. The viscoelastic solid is modeled with two non-linear constitutive equations, first combining a neo-Hookean spring with a dashpot in parallel (a non-linear Kelvin-Voigt type model) and second a neo-Hookean spring with an upper convective Maxwell element in parallel. We investigate the effects of fluid viscosity and substrate viscoelasticity on its deformation and the force on the rigid sphere.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.
| Thumbnail | Title | Date Uploaded | Visibility | Actions |
|---|---|---|---|---|
|
|
Tarafder_gwu_0075A_16757.pdf | 2024-10-02 | Open Access |
|