arXiv subjects

Parameshwaran A

Publications and source records attributed to Parameshwaran A.

5 recordsLinked to original sources

arXiv2026

Active alignment-driven coarsening in confined near-critical fluids

We investigate vapor-liquid phase separation of an active near critical Lennard-Jones fluid confined within a cylindrical pore using molecular dynamics simulations. Activity is introduced via Vicsek-type alignment interactions, enabling a systematic study of how self-propulsion modifies domain morphology and coarsening kinetics under quasi-one-dimensional confinement. In the passive limit, the system undergoes early-time spinodal decomposition (diffusive growth characterized by the Lifshitz-Slyozov exponent $\alpha = 1/3$), followed by the formation of periodically modulated, plug-like liquid domains along the pore axis. At late times, coarsening becomes kinetically arrested, and the system remains trapped in a metastable striped state. Introducing activity destabilizes this arrested morphology by enhancing collective domain transport, leading to frequent domain mergers and complete phase separation at sufficiently high activity. The late-stage coarsening then exhibits a crossover to faster, ballistic growth with an effective exponent $\alpha = 2/3$, consistent with a cluster-coalescence mechanism. Analysis of two-point correlation functions and structure factors confirms dynamic scaling across all activity regimes. Our results demonstrate that alignment-induced activity can overcome confinement-driven kinetic arrest, providing new insight into phase separation in confined active fluids. The relevant growth laws are analyzed and interpreted using appropriate theoretical frameworks.

cond-mat.soft↗

arXiv2025

Breaking the Logarithmic Barrier: Activity-Induced Recovery of Phase Separation Dynamics in Confined Geometry

Phase separation in confined environments is a fundamental process underlying geological flows, porous filtration, emulsions, and intracellular organization. Yet, how confinement and activity jointly govern coarsening kinetics and interfacial morphology remains poorly understood. Here, we use large-scale molecular dynamics simulations to investigate vapor-liquid phase separation of passive and active fluids embedded in complex porous media. By generating porous host structures via a freeze-quench protocol, we systematically control the average pore size and demonstrate that confinement induces a crossover from the Lifshitz-Slyozov power-law growth to logarithmically slowed coarsening, ultimately arresting domain evolution. Analysis of correlation functions and structure factors reveals that confined passive systems exhibit fractal interfaces, violating Porod's law and indicating rough morphological arrest. In contrast, introducing self-propulsion dramatically changes the coarsening pathway: activity restores smooth interfaces, breaks the confinement-induced scaling laws, and drives a transition from logarithmic to ballistic domain growth at high activity levels. Our findings reveal an activity-controlled mechanism to overcome geometric restrictions and unlock coarsening in structurally heterogeneous environments. These insights establish a unifying framework for nonequilibrium phase transitions in porous settings, with broad relevance to active colloids, catalytic media, and biologically crowded systems, where living matter routinely reorganizes within geometric constraints to sustain function.

cond-mat.soft↗

arXiv2025

Viscous Growth Law in Bubble Coarsening: A Molecular Dynamics Perspective

We investigate the kinetics of bubble coarsening in a single component Lennard-Jones fluid using large-scale molecular dynamics simulations. A homogeneous high-temperature system is quenched below the critical temperature to induce the nucleation and growth of vapor bubbles within a dense liquid matrix. The structural evolution is characterized by two point correlation functions and the static structure factor, both of which exhibit dynamic scaling and sharp interfaces consistent with Porod law. The time-dependent characteristic length scale, extracted from the correlation function, shows a robust power law growth $\ell(t) \sim t^{\alpha}$. Finite size scaling analysis across different system sizes yields $\alpha \approx 1.0$, establishing that coarsening is dominated by viscous hydrodynamic interactions rather than classical diffusion-limited Ostwald ripening predicted by the Lifshitz-Slyozov-Wagner theory. These results provide atomistic evidence for fluid flow controlled coarsening in vapor-liquid systems and emphasize the need to go beyond diffusion-based theories to describe bubble dynamics in dense fluids.

cond-mat.soft↗

arXiv2024

Phase separation and rheology of segregating binary fluid under shear

We employ molecular dynamics simulation to study the phase separation and rheological properties of a three-dimensional binary liquid mixture with hydrodynamics undergoing simple shear deformation. The impact of shear intensity on domain growth is investigated, with a focus on how shear primarily distorts the domains, leading to the formation of anisotropic structures. The structural anisotropy is quantified by evaluating domain sizes along the flow and shear direction. The rheological properties of the system is studied in terms of shear stress and excess viscosity. At low shear rates, the system behaves like a Newtonian fluid. However, the strong-shear case is marked by a transition characterized by non-Newtonian behavior.

cond-mat.soft↗

arXiv2024

Kinetics of vapor-liquid transition of active matter system under quasi one-dimensional confinement

We study the kinetics of vapor-liquid phase separation in a quasi one-dimensional confined active matter system using molecular dynamics simulations. Activity is invoked via the Vicsek rule, while passive interaction follows the Lennard-Jones potential. With the system density near the vapor branch, the evolution morphology features disconnected liquid clusters. In the passive limit, coarsening begins with nucleation, followed by an evaporation-condensation growth mechanism, leading to a metastable state without complete phase separation. We aim to understand the impact of Vicsek-like self-propulsion on the structure and growth of these clusters. Our key finding is that Vicsek activity results in a distinct growth mechanism, notably rapid cluster growth and the breakdown of the metastable state through ballistic aggregation. Relevant growth laws are analyzed and explained using appropriate theoretical models.

cond-mat.soft↗