arXiv subjects

Manaswita Bose

Publications and source records attributed to Manaswita Bose.

3 recordsLinked to original sources

arXiv2026

Energy non-equipartition in vibrofluidized particles

The aim of the present work is to investigate the influence of the realistic model parameters for particle interactions, specifically the spring stiffness coefficient for the tangential force between particles on the energy equipartition in a vibrofluidized system. To achieve this, a three-dimensional vertically vibrated granular system consisting of spherical particles is simulated using the discrete element method (DEM) implemented in the open-source software LAMMPS. Interparticle and wall-particle interactions are determined using the linear-spring dashpot model. Simulations are performed for particles ranging from nearly perfectly smooth to nearly perfectly rough. Two different values for the ratio of the tangential to normal spring stiffness coefficient $κ$ ($2/7$ and $3/4$) are chosen for most of the simulations. The ratio of the translational to the rotational kinetic energy ($K$) monotonically decreases with an increase in the friction coefficient, $μ$ for $κ=2/7$; however, for $κ= 3/4$, after an initial reduction with $μ$, $K$ increases and plateaus at $\approx 5$, indicating the absence of equipartition of energy between the translational and rotational modes. Further simulations performed for $0.67 \le κ< 1$ confirm non-equipartition of energy for particles with a very high friction coefficient.

cond-mat.soft↗

arXiv2025

Evaluation of Turbulence Models and Boundary Conditions for Hybrid Ventilation in Reduced-scale Classroom Model

In this paper, we study the ventilation airflow in a model classroom, where exhaust fans throw out the used air, to replace it with outdoor air through open door. Hybrid ventilation, or mechanically assisted natural ventilation, of this kind is used as a retrofit design to reduce infection risk from airborne transmission. The air stream entering the door forms a jet-like flow, driven by the suction effect of exhaust fans. We compute the jet velocity using Reynolds averaged Navier Stokes (RANS) method and compare with velocity field measured using particle image velocimetry. Different turbulence models are found to match experimental data near the door, but they over-predict the peak jet velocity further downstream. There is minimal variation between the results obtained using different turbulence models. The computational results are found to be sensitive to inlet boundary conditions, whether the door entry is specified as a pressure inlet or velocity inlet. The geometry of the space outside the door also has a significant effect on the jet velocity. Changing the boundary condition takes the computational results closer to the experimental data; the velocity profiles computed with the extended domain being the closest to the measured peak velocity. Interestingly, the centerline velocity decay computed with the extended domain aligns well with the experimental data. The other cases, irrespective of turbulence model, show much lower decay rate that seem to align with wall jet scaling. This suggests that geometry and boundary conditions at the door is critical to predict the airflow in hybrid ventilation.

physics.flu-dyn↗

arXiv2024

Role of the ratio of tangential to normal stiffness coefficient on the behaviour of vibrofluidised particles

The selection of parameters in the contact law for inter-particle interactions affects the results of simulations of flowing granular materials. The present study aims to understand the effect of the ratio of tangential to normal spring stiffness coefficient ($κ$) on inter-particle contact behaviour in terms of the rotational coefficient of restitution determined using data obtained from multi-particle simulations. The effect of $κ$ on the profiles of the micro- and macroscopic properties of particles in a vibrofluidised bed is also investigated. The Discrete Element Method (DEM) is used to simulate a vertically vibrated fluidised bed using the open-source software LAMMPS. The inter-particle and wall-particle contact forces are determined using the linear spring-dashpot (LSD) model. The distribution of the mean co-ordination number, force during the contact, contact regimes, and rotational coefficient of restitution are determined from the data obtained from simulations. It was shown that $κ$ plays a significant role in the distribution of inter-particle contacts between different regimes and, thereby, the velocity distribution and profiles of statistically averaged properties of the vibrofluidised particles. Our results show that for particles with surface friction coefficient $μ>0.1$, the commonly used value $κ=\frac{2}{7}$ results in quantitatively different results from those obtained using $0.67 \le κ< 1$, a range consistent with the realistic values of Poisson ratios for simple materials.

cond-mat.soft↗