Intermolecular And Surface Forces

A critical evaluation of force term in lattice Boltzmann method, natural convection problem

Lattice Boltzmann method for MHD natural convection heat transfer using nanofluid

Computational methods have been extended recently to allow for the presence of moving contact lines in simulated two-phase flows. The predictive capability offered by these methods is potentially large, joining theoretical and experimental methods. Several challenges rather unique to this area need to be overcome, however, notably regarding the conditions near a moving contact line and the very large separation of length scales in these flows. We first summarize the main models for moving contact lines and follow with an overview of computational methods that includes direct continuum approaches and macroscale models that resolve only the large-scale flow by modeling the effects of the conditions near the contact line using theory. Results are presented for contact-line motion on ideal as well as patterned and grooved surfaces and for extensions to account for complexities such as thermocapillarity and phase change.

Numerical Simulations of Flows with Moving Contact Lines

Numerical simulations of 3D flows with moving contact lines

https://www.iith.ac.in/~hdixit/papers/dixit_babu_lbm_cavity.pdf

Simulation of high Rayleigh number natural convection in a square cavity using the lattice Boltzmann method

We study the classical Landau–Levich dip-coating problem in the case where the interface has significant elasticity. One aim of this work is to unravel the effect of surface-adsorbed hydrophobic particles on Landau–Levich flow. Motivated by recent findings (Vella, Aussillous & Mahadevan, Europhys. Lett., vol. 68, 2004, pp. 212–218) that a jammed monolayer of adsorbed particles on a fluid interface makes it respond akin to an elastic solid, we use the Helfrich elasticity model to study the effect of interfacial elasticity on Landau–Levich flow. We define an elasticity number, , which represents the relative strength of viscous forces to elasticity. The main assumptions of the theory are that be small, and that surface tension effects are negligible. The shape of the free surface is formulated as a nonlinear boundary value problem: we develop the solution as an asymptotic expansion in the small parameter and use the method of matched asymptotic expansions to determine the film thickness as a function of . The solution to the shape of the static meniscus is not as straightforward as in the classical Landau–Levich problem, as evaluation of higher-order effects is necessary in order to close the problem. A remarkable aspect of the problem is the occurrence of multiple solutions, and five of these are found numerically. In any event, the film thickness varies as in qualitative agreement with the experiments of Ouriemi & Homsy (Phys. Fluids, 2013, in press).

The elastic Landau–Levich problem

In this study, we develop a systematic perturbation procedure in the small parameter, B1/2, where B is the Bond number, to study capillary effects on small cylindrical particles at interfaces. Such a framework allows us to address many problems involving particles on flat and curved interfaces. In particular, we address four specific problems: (i) capillary attraction between cylinders on flat interface, in which we recover the classical approximate result of Nicolson [“The interaction between floating particles,” Proc. Cambridge Philos. Soc. 45, 288–295 (1949)10.1017/S0305004100024841], thus putting it on a rational basis; (ii) capillary attraction and aggregation for an infinite array of cylinders arranged on a periodic lattice, where we show that the resulting Gibbs elasticity obtained for an array can be significantly larger than the two cylinder case; (iii) capillary force on a cylinder floating on an arbitrary curved interface, where we show that in the absence of gravity, the cylinder experiences a...

/pdf/capillary-effects-on-floating-cylindrical-particles-3g20vsyjhk.pdf

Capillary effects on floating cylindrical particles

The flow past inline oscillating rectangular cylinders is studied numerically at a Reynolds number representative of two-dimensional flow. A symmetric mode, known as S-II, consisting of a pair of oppositely-signed vortices on each side, observed recently in experiments, is obtained computationally. A new symmetric mode, named here as S-III, is also found. At low oscillation amplitudes, the vortex shedding pattern transitions from antisymmetric to symmetric smoothly via a regime of intermediate phase. At higher amplitudes, this intermediate regime is chaotic. The finding of chaos extends and complements the recent work of Perdikaris et al. [1]. Moreover it shows that the chaos results from a competition between antisymmetric and symmetric shedding modes. Rectangular cylinders rather than square are seen to facilitate these observations. A global, and very reliable, measure is used to establish the existence of chaos.

Vortex shedding patterns, their competition, and chaos in flow past inline oscillating rectangular cylinders

Coupling between voltage and tip-to-collector distance in polymer electrospinning: Insights from analysis of regimes, transitions and cone/jet features

Harish N. Dixit

Papers

Simulation of high Rayleigh number natural convection in a square cavity using the lattice Boltzmann method

The elastic Landau–Levich problem

Capillary effects on floating cylindrical particles

Vortex shedding patterns, their competition, and chaos in flow past inline oscillating rectangular cylinders

Coupling between voltage and tip-to-collector distance in polymer electrospinning: Insights from analysis of regimes, transitions and cone/jet features