arXiv subjects

Alexander L. Yarin

Publications and source records attributed to Alexander L. Yarin.

4 recordsLinked to original sources

arXiv2026

An improved phase-field framework for simulating impacts of solidifying metal drops

Here, an improved phase-field method for simulating the impact dynamics of solidifying molten metal droplets is developed using targeted free-energy modifications. Conventional Cahn-Hilliard-Navier-Stokes (CHNS) formulations generally do not capture melt retraction over a solidified portion of the droplet, because the newly formed solid region is not treated as an actual internal boundary in a single-order-parameter diffuse-interface model. As a result, the formulation lacks an internal wetting condition or localized wall-energy mechanism capable of driving melt retraction over a solidified splat. To address this limitation, a diffuse-domain wall-energy term is added to the free energy, with a chemical-potential contribution that is active near the diffuse liquid-solidified-material-gas triple-line region, enabling the remaining melt to retract over a solidified splat. In addition, a solidification penalty term is introduced to immobilize the solidified splat formed during impact and suppress unphysical interface motion caused by residual Cahn-Hilliard diffusion inside the frozen region. The proposed formulation is validated against benchmark experiments on impacts of solidifying tin droplets. The results reveal that the localized wall-energy term captures post-maximum-spread melt retraction, while the penalty term effectively arrests motion of the solidified splat. Qualitative and quantitative comparisons with experiments, volume-of-fluid simulations, and standard phase-field predictions demonstrate that the proposed formulation captures post-maximum-spread melt retraction and provides an accurate estimate of the stabilized final splat diameter.

physics.flu-dyn↗

arXiv2025

On the Energy Analysis of Two-phase Flows Simulated with the Diffuse Interface Method

The Phase-Field Method (PFM) is employed to simulate two-phase flows with the fully-coupled Cahn-Hilliard-Navier-Stokes (CHNS) equations governing the temporal evolution. The methodology minimizes the total energy functional, accounting for diffusive and viscous dissipations. A new perspective is presented by analyzing the interplay between kinetic energy, mixing energy, and viscous dissipation using the temporal evolution of the total energy functional. The classical surface energy is approximated with mixing energy under specific conditions, and the accuracy of this substitution is rigorously evaluated. The energy-based surface tension formulation derived from the Korteweg stress tensor demonstrates exceptional accuracy in capturing variations in the mixing energy. These concepts are demonstrated by considering two benchmark problems: droplet oscillation and capillary thread breakup. Key findings include validating mixing-energy theory for highly deformed interfaces, as well as the discovery of distinct energy dissipation patterns during thread breakup and droplet oscillations. The results highlight the robustness of the free energy-based PFM in accurately capturing complex interfacial dynamics, while maintaining energy conservation.

physics.flu-dyn↗

arXiv2023

Models of polymer solutions in electrified jets and solution blowing

Fluid flows hosting electrical phenomena make the subject of a fascinating and highly interdisciplinary scientific field. In recent years, the extraordinary success of electrospinning and solution blowing technologies for the generation of polymer nanofibers has motivated vibrant research aiming at rationalizing the behavior of viscoelastic jets under applied electric fields or other stretching fields including gas streams. Theoretical models unveiled many original aspects in the underpinning physics of polymer solutions in jets, and provided useful information to improve experimental platforms. This article reviews advances in the theoretical description and numerical simulation of polymer solution jets in electrospinning and solution blowing. Instability phenomena of electrical and hydrodynamic origin are highlighted, which play a crucial role in the relevant flow physics. Specifications leading to accurate and computationally viable models are formulated. Electrohydrodynamic modeling, theories for the jet bending instability, recent advances in Lagrangian approaches to describe the jet flow, including strategies for dynamic refinement of simulations, and effects of strong elongational flow on polymer networks are reviewed. Finally, the current challenges and future perspectives of the field are outlined and discussed, including the task of correlating the physics of the jet flows with the properties of realized materials, as well as the development of multiscale techniques for modelling viscoelastic jets.

physics.flu-dyn↗

arXiv2021

Drop impact onto a substrate wetted by another liquid: Corona detachment from the wall film

Drop impact onto a thin liquid film of another liquid is observed and characterized using a high-speed video system. A new mode of splash - a complete, simultaneous corona detachment - has been observed, which is the result of the lamella breakup near the wall film. The abrupt outward and upward displacement of the lamella leads to an extreme stretching of the corona wall, resulting in rapid thinning and a rupture of the corona wall. This rupture triggers propagating Taylor-Culick rims, which rapidly spread, meet and thus undercut simultaneously the entire corona, resulting in its detachment. Special experiments with the spreading corona impingement onto a fixed needle, supplement the physical evidence of the above-mentioned mechanism. A self-consistent theory of the observed phenomena is proposed and compared with experiments, exhibiting good agreement.

physics.flu-dyn↗