arXiv subjects

Afsoun Rahnama Falavarjani

Publications and source records attributed to Afsoun Rahnama Falavarjani.

2 recordsLinked to original sources

arXiv2022

Modeling Droplets with Slippery Interfaces

Many multiphase fluid systems, such as those involving immiscible polymers or liquid-liquid systems with surfactants, have shown a breakdown of the no-slip condition at the material interface. This results in systems where the tangential velocity of the inner and outer fluid can differ, with the jump in velocity dependent not only the material properties of the interface but also the stresses applied by the surrounding fluid. In this work a numerical model is presented which is capable of investigating general multiphase fluid systems involving interfacial slip in both two- and three-dimensions. To make the system computationally feasible, a hybrid Navier-Stokes projection method is used, whereby the viscosity, density, and pressure are assumed to be continuous across the interface while the velocity field can experience a jump, which is handled via the Immersed Interface Method. The numerical model is compared to experimental results involving polymer-polymer mixtures and computational results for droplets in extensional flows, showing excellent agreement with both. It is then used to explore the influence of interfacial slip in a number of common multiphase fluid systems, including the shearing of a planar interface, droplet and filament relaxation, and droplets in shear flow, both unbounded and wall-bound.

physics.flu-dyn↗

arXiv2020

Non-equilibrium dynamics of initially spherical vesicles in general flow

Many vesicles have a spherical resting shape and exposure to fluid flows induces an exchange between sub-optical area and visible (systematic) deformation, while the total area is conserved. The dynamics which controls the exchange between sub-optical and visible area depends on membrane properties such as bending rigidity and initial tension. Conversely, observation of these dynamics can be used to determine the membrane properties. The goal of this work is to create a general numerical model which accounts for the exchange between sub-optical and visible area. Unlike prior modeling efforts, the model does not pre-assume a shape type, such as nearly-spherical, or applied flow field, allowing the model to capture a wider variety of flow conditions. Based on implicit interface tracking and using a volume-preserving multiphase Navier-Stokes solver, the model is compared to several experimental results, showing excellent agreement. It is used to explore regimes not possible with previously published models, such as the variable viscosity case, and how these system properties influence experimentally measurable parameters such as deformation parameter. By creating a more generalized framework for the modeling of vesicles with sub-optical area, it will now be possible to make predictions on vesicle material properties from a wider variety of experimental results.

cond-mat.soft↗