https://libjncir.jncasr.ac.in/xmlui/handle/10572/1492 2026-04-04T05:31:28Z 2026-04-04T05:31:28Z Ahmad, Shaista Puri, Sanjay Das, Subir Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2545 2017-02-21T10:25:26Z 2014-01-01T00:00:00Z

Phase separation of fluids in porous media: A molecular dynamics study Ahmad, Shaista; Puri, Sanjay; Das, Subir Kumar We present comprehensive molecular dynamics results for phase-separation kinetics of fluids in a porous medium. This system is modeled by a symmetric Lennard-Jones fluid mixture with a quenched random field. The presence of disorder slows down domain growth from power-law to a logarithmic form. It also modifies the correlation functions and structure factors which characterize the morphology. In particular, the structure-factor tail shows a non-Porod behavior, which is the consequence of scattering from rough interfaces. Restricted Access

2014-01-01T00:00:00Z Midya, Jiarul Majumder, Suman Das, Subir Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2541 2017-02-21T10:25:25Z 2014-01-01T00:00:00Z

Aging in ferromagnetic ordering: full decay and finite-size scaling of autocorrelation Midya, Jiarul; Majumder, Suman; Das, Subir Kumar Nonequilibrium dynamics in Ising and Ginzburg-Landau models were studied for a nonconserved order parameter that mimics ordering in ferromagnets. The focus was on the understanding of the decay of the two time (t, tw; t > t(w)) order-parameter correlation function. For this quantity, a full form has been obtained empirically which, for t >> t(w), provides a power-law similar to (l/l(w)) (lambda), l and l(w) being the characteristic lengths at t and t(w), respectively. This empirical form was used for a finite-size scaling analysis to obtain the exponent lambda in space dimensions d = 2 and 3. Our estimates of lambda and understanding of the finite-size effects, for the models considered, provide useful information on the relevance of thermal noise. The values of lambda obtained are in good agreement with the predictions of a theory based on Gaussian auxiliary field ansatz. Restricted Access

2014-01-01T00:00:00Z Paul, Subhajit Das, Subir Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2542 2017-02-21T10:25:28Z 2014-01-01T00:00:00Z

Dynamics of clustering in freely cooling granular fluid Paul, Subhajit; Das, Subir Kumar Via the event-driven molecular-dynamics simulations, we have studied the structure and dynamics in a model granular fluid of hard discs in space dimension d = 2. Inelastic collisions among these discs lead to clustering, resembling the kinetics in a vapor-liquid phase transition. The structural growth of these clusters are quantified via an application of finite-size scaling theory. We also present results for the decay of the kinetic energy. Discussion on the validity of a scaling argument, connecting the latter with the time dependence of clustering, is provided. Further, a striking difference in the finite-size effects of the kinetics with those of the phase transition dynamics is pointed out. Copyright (C) EPLA, 2014 Restricted Access

2014-01-01T00:00:00Z Roy, Sutapa Das, Subir Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2543 2017-02-21T10:25:32Z 2014-01-01T00:00:00Z

Finite-size scaling study of shear viscosity anomaly at liquid-liquid criticality Roy, Sutapa; Das, Subir Kumar We study the equilibrium dynamics of a symmetrical binary Lennard-Jones fluid mixture near its consolute criticality. Molecular dynamics simulation results for the shear viscosity,., from a micro-canonical ensemble are compared with those from a canonical ensemble with various thermostats. It is observed that the Nose-Hoover thermostat is a good candidate for this purpose, and is therefore adopted for the quantification of the critical singularity of., to avoid the temperature fluctuations (or even drifts) that are often encountered in microcanonical simulations. Via a finite-size scaling analysis of our simulation data we have been able to confirm that the shear viscosity exhibits a weak critical singularity in agreement with the theoretical predictions. (C) 2014 AIP Publishing LLC. Restricted Access

2014-01-01T00:00:00Z