arXiv subjects

Prapanch Nair

Publications and source records attributed to Prapanch Nair.

9 recordsLinked to original sources

arXiv2026

A numerical study on the coefficient of restitution of wet collisions

Using smoothed particle hydrodynamics (SPH) simulations, we investigate the coefficient of restitution (COR) in wet collisions and identify a scaling law governing its behavior. The simulations employ an updated-Lagrangian, mesh-free framework that is validated against experimental measurements. We neglect surface tension effects since the impact conditions correspond to a moderate-to-high Weber number regime. The COR is found to depend on the Stokes number and a dimensionless film thickness defined as the ratio of the liquid film thickness to the diameter of the impacting solid bead. Two distinct regimes are observed, each characterized by different power-law exponents.

physics.flu-dyn↗

arXiv2026

A numerical study on the effect of rolling friction on clogging of pores in particle-laden flows

Particulate matter in a fluid injected into a porous reservoir impairs its permeability spatio-temporally due to pore clogging. As particle volume fraction increases near the pore throats, inter-particle contact mechanics determine their jamming and subsequent pore clogging behavior. During contact of particles submerged in a fluid, in addition to sliding friction, a rolling resistance develops due to a several micromechanical and hydrodynamic factors. A coefficient of rolling friction is often used as a lumped parameter to characterize particle rigidity, particle shape, lubrication and fluid mediated resistance, however its direct influence on the clogging behavior is not well studied in literature. We study the effect of rolling resistance on the clogging behavior of a dense suspension at pore scale using direct numerical simulations (DNS). A discrete element method (DEM) library is developed and coupled with an open-source immersed boundary method (IBM) based solver to perform pore and particle resolved simulations. Several 3D validations are presented for the DEM library and the DEM-IBM coupling and the effect of rolling resistance on clogging at a pore entry is studied.

physics.flu-dyn↗

arXiv2025

A three-dimensional numerical scheme for modeling three-phase contact line pinning using Smoothed Particle Hydrodynamics

In several capillary dynamics experiments, the liquid domain is confined by pinning the three-phase contact line along a sharp edge or a discontinuity on the substrate. Simulating the dynamics of pinned droplets can offer valuable insights into capillary flow phenomena involving wetting of inhomogeneous substrates. However, Eulerian multi-phase flow solvers are usually not able to directly implement pinning of three-phase contact lines. We present the implementation of a model for pinning the contact line of a liquid along an arbitrary pinning curve on the substrate, in an updated Lagrangian, meshless flow solver based on the smoothed particle hydrodynamics (SPH) method. We develop the pinning model for a continuum surface force scheme and assume a free surface for the liquid-gas interface. We validate the model against several capillary dynamics experiments involving pinned three phase contact lines with fixed and dynamic substrates to demonstrate the robustness and accuracy of the solver.

physics.flu-dyn↗

arXiv2024

An Eulerian Meshless Method for Two-phase Flows with Embedded Geometries

We present a novel Eulerian meshless method for two-phase flows with arbitrary embedded geometries. The spatial derivatives are computed using the meshless generalized finite difference method (GFDM). The sharp phase interface is tracked using a volume fraction function. The volume fraction is advected using a method based on the minimisation of a directional flux-based error. For stability, the advection terms are discretised using upwinding schemes. In the vicinity of the embedded geometries, the signed distance function is used to populate the surface of the geometries to generate a body-conforming point cloud. Consequently, the points on the boundaries participate directly in the discretisation, unlike conventional immersed-boundary methods where they are either used to calculate momentum deficit (for example, continuous forcing) or conservation losses (for example, cut-cell methods). The boundary conditions are, therefore, directly imposed at these points on the embedded geometries, opening up the possibility for a discretisation that is body-conforming and spatially varying in resolution, while retaining the consistency of the scheme. We present benchmark test cases that validate the method for two-phase flows, flows with embedded boundaries and a combination of both.

physics.flu-dyn↗

arXiv2023

Surface tension and wetting at free surfaces in Smoothed Particle Hydrodynamics

Surface tension and wetting are dominating physical effects in micro and nanoscale flows. We present an efficient and reliable model of surface tension and equilibrium contact angles in Smoothed Particle Hydrodynamics for free-surface problems. We demonstrate its robustness and accuracy by simulating several notoriously difficult three-dimensional free surface flow problems driven by interfacial tension.

physics.flu-dyn↗

arXiv2020

Can Minkowski tensors of a porous microstructure characterize its permeability?

We show that the permeability of porous media can be reliably predicted from the Minkowski tensors (MTs) describing the pore microstructure geometry. To this end, we consider a large number of simulations of flow through periodic unit cells containing complex shaped obstacles. The prediction is achieved by training a deep neural network (DNN) using the simulation data with the MT elements as attributes. The obtained predictions allow for the conclusion that MTs of the pore microstructure contain sufficient information to determine the permeability, although the functional relation between the MTs and the permeability could be complex to determine.

physics.flu-dyn↗

arXiv2018

Influence of capillary viscous flow on melting dynamics

The rate of melting of a solid and the rate of deformation of the resulting melt due to capillary forces are comparable in additive manufacturing applications. This dynamic structural change of a melting solid is extremely challenging to study experimentally. Using meshless numerical simulations we show the influence of the flow of the melt on the heat transfer and resulting phase change. We introduce an accurate and robust Incompressible Smoothed Particle Hydrodynamics method to simulate melting of solids and the ensuing fluid-solid interaction. We present validation for the heat transfer across free surface and the melting interface evolution, separately. We then present two applications for this coupled multiphysics simulation method---the study of rounding of an arbitrarily shaped particle during melting and the non-linear structural evolution of three spheres undergoing agglomeration. In both the studies we use realistic transport and thermal properties for the materials so as to demonstrate readiness of the method for solving engineering problems in additive manufacturing.

physics.comp-ph↗

arXiv2018

Multiphase flows with compressible and incompressible phases

Gas bubbles immersed in a liquid and flowing through a large pressure gradient undergoes volumetric deformation in addition to possible deviatoric deformation. While the high density liquid phase can be assumed to be an incompressible fluid, the gas phase needs to be modelled as a compressible fluid for such bubble flow problems. The Rayleigh--Plesset (RP) equation describes such a bubble undergoing volumetric deformation due to changes in pressure in the ambient incompressible fluid, assuming axisymmetric dynamics. We propose a compressible-incompressible coupling of Smoothed Particle Hydrodynamics (SPH) and validate this coupling against the RP model in two dimensions. For different density ratios, a sinusoidal pressure variation is applied to the ambient incompressible liquid and the response of the bubble is observed and compared with the solutions of the axisymmetric RP equation.

physics.comp-ph↗

arXiv2017

Dynamic capillary phenomena using Incompressible SPH

Grid based fluid simulation methods are not able to monolithically capture complex non-linear dynamics like the rupture of a dynamic liquid bridge between freely colliding solids, an exemplary scenario of capillary forces competing with inertial forces in engineering applications. We introduce a new Incompressible Smoothed Particle Hydrodynamics method for simulating three dimensional fluid-solid interaction flows with capillary (wetting and surface tension) effects at free surfaces. This meshless approach presents significant advantages over grid based approaches in terms of being monolithic and in handling interaction with free solids. The method is validated for accuracy and stability in dynamic scenarios involving surface tension and wetting. We then present three dimensional simulations of crown forming instability following the splash of a liquid drop, and the rupture of a liquid bridge between two colliding solid spheres, to show the method's advantages in the study of dynamic micromechanical phenomena involving capillary flows.

physics.comp-ph↗