Surface force at the nano-scale: observation of non-monotonic surface tension and disjoining pressure

2015 ◽  
Vol 17 (32) ◽  
pp. 20502-20507 ◽  
Author(s):  
Tiefeng Peng ◽  
Mahshid Firouzi ◽  
Qibin Li ◽  
Kang Peng
Keyword(s):  
Surface Tension ◽  
Surface Force ◽  
Md Simulations ◽  
Disjoining Pressure ◽  
Nano Scale ◽  
Disjoining Pressures

The disjoining pressures of thin aqueous salt films at different salt concentrations and temperatures were calculated using MD simulations.

scholarly journals Comparison of Surface Tension Models for the Volume of Fluid Method

Processes ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 542 ◽  
Author(s):  
Kurian J. Vachaparambil ◽  
Kristian Etienne Einarsrud
Keyword(s):  
Surface Tension ◽  
Multiphase Flow ◽  
Capillary Rise ◽  
Surface Tension Force ◽  
Surface Force ◽  
Parallel Plates ◽  
Time Step ◽  
Mesh Resolution ◽  
Active Research ◽  
Spurious Currents

With the increasing use of Computational Fluid Dynamics to investigate multiphase flow scenarios, modelling surface tension effects has been a topic of active research. A well known associated problem is the generation of spurious velocities (or currents), arising due to inaccuracies in calculations of the surface tension force. These spurious currents cause nonphysical flows which can adversely affect the predictive capability of these simulations. In this paper, we implement the Continuum Surface Force (CSF), Smoothed CSF and Sharp Surface Force (SSF) models in OpenFOAM. The models were validated for various multiphase flow scenarios for Capillary numbers of 10 − 3 –10. All the surface tension models provide reasonable agreement with benchmarking data for rising bubble simulations. Both CSF and SSF models successfully predicted the capillary rise between two parallel plates, but Smoothed CSF could not provide reliable results. The evolution of spurious current were studied for millimetre-sized stationary bubbles. The results shows that SSF and CSF models generate the least and most spurious currents, respectively. We also show that maximum time step, mesh resolution and the under-relaxation factor used in the simulations affect the magnitude of spurious currents.

scholarly journals Succinic acid in aqueous solution: connecting microscopic surface composition and macroscopic surface tension

2014 ◽  
Vol 16 (39) ◽  
pp. 21486-21495 ◽  
Author(s):  
Josephina Werner ◽  
Jan Julin ◽  
Maryam Dalirian ◽  
Nønne L. Prisle ◽  
Gunnar Öhrwall ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Surface Tension ◽  
Succinic Acid ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Md Simulations ◽  
Vapor Interface ◽  
X Ray ◽  
Ph Values ◽  
Microscopic Surface

The water–vapor interface of aqueous solutions of succinic acid, where pH values and bulk concentrations were varied, has been studied using surface sensitive X-ray photoelectron spectroscopy (XPS) and molecular dynamics (MD) simulations.

Comparison of Surface Tension Models in Smoothed Particles Hydrodynamics Method

2019 ◽  
Author(s):  
Lijing Yang ◽  
Milad Rakhsha ◽  
Dan Negrut
Keyword(s):  
Surface Tension ◽  
Liquid Droplet ◽  
Surface Force ◽  
Accurate Estimation ◽  
Droplet Deformation ◽  
Two Phase ◽  
Mesh Free ◽  
Interface Curvature ◽  
Particle Force ◽  
Smoothed Particles Hydrodynamics

Abstract We compare two surface tension models to solve two-phase fluid interaction problems in the context of the mesh-free Smoothed Particles Hydrodynamics (SPH) method. The Continuum Surface Force (CSF) model (later extended to Continuum Surface Stress, CSS), originally derived from grid-based numerical methods, requires an accurate estimation of the interface curvature to express the surface tension. Unlike CSF, the Inter-Particle Force (IPF) model is more robust in this regard as it draws on a molecular dynamics foundation by considering how the pairwise interaction forces between particles within a cutoff distance act in relation to producing the surface tension. Herein, we rely on second-order consistent gradient and Laplacian operators to improve the accuracy of SPH formulations as well as on a particle shifting technique to “disorder” particles from non-differentiable interface geometries. A 3D liquid droplet deformation test is used to compare CSF and IPF in terms of their pressure field and kinetic energy dissipation accuracy.

New Frontiers of Micro and Nano-Scale Thermophysical Properties Sensing

2007 ◽  
Author(s):  
Yuji Nagasaka
Keyword(s):  
Thermal Conductivity ◽  
Surface Tension ◽  
Diffusion Coefficient ◽  
Thermal Diffusivity ◽  
Thermophysical Properties ◽  
Industrial Applications ◽  
Optical Techniques ◽  
Nano Scale ◽  
Measurement Tools ◽  
Keynote Speech

The present keynote speech overviews new frontiers of sensing techniques for thermophysical properties in micro and nano-scale processes which are being developed at Keio. Especially, new optical sensing techniques to measure wide variety of thermophysical properties such as thermal diffusivity, thermal conductivity, viscosity, mass diffusion coefficient and surface tension of novel fluids and solids in micro and nano-scale are presented with an emphasis on their industrial applications. All of these new optical techniques have high spatial and temporal resolutions which have never been attained by other conventional measurement tools.

Molecular Dynamics Simulations and Theory of Interfaces of Oligomers

1992 ◽  
Vol 291 ◽  
Author(s):  
Jonathan G. Harris ◽  
Yantse Wang
Keyword(s):  
Surface Tension ◽  
Glassy State ◽  
Surface Force ◽  
Molecular Motions ◽  
Molecular Fluids ◽  
Force Microscopy ◽  
Atomic Force ◽  
Branched Alkanes ◽  
Dynamics Simulations ◽  
Solvation Forces

ABSTRACTThese proceedings summarize recent work in our group studying the structure of interfaces involving molecular fluids. Two types of systems are discussed. First, we summarize simulations of the structure and surface tension of liquid-vapor interfaces of the alkanes eicosane and decane. Then, we describe the results of simulations of the confined films studied in surface force apparatus and atomic force microscopy experiments. Our simulations show that in both films of normal and branched alkanes, the formation of a layered structure is observed. The branching inhibits this layering, especially in the narrowest pores. In addition an examination of the molecular motions indicates that a transition to a solid or glassy state is not a prerequisite for layering or oscillating solvation forces.

Surface Tension Evaluation Via Thermodynamic Analysis of Statistical Data From Molecular Dynamics Simulations

Volume 4 ◽  
2004 ◽  
Author(s):  
Aaron P. Wemhoff ◽  
Van P. Carey
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Density Profile ◽  
Md Simulation ◽  
Md Simulations ◽  
Bulk Liquid ◽  
Interfacial Region ◽  
Lennard Jones Potential ◽  
Jones Potential ◽  
Lennard Jones

Surface tension determination of liquid-vapor interfaces of polyatomic fluids using traditional methods has shown to be difficult due to the requirement of evaluating complex intermolecular potentials. However, analytical techniques have recently been developed that determine surface tension solely by means of the characteristics of the interfacial region between the bulk liquid and vapor regions. A post-simulation application of the excess free energy density integration (EFEDI) method was used for analysis of the resultant density profile of molecular dynamics (MD) simulations of argon using a simple Lennard-Jones potential and diatomic nitrogen using a two-center Lennard-Jones potential. MD simulations were also run for an approximation of nitrogen using the simple Lennard-Jones potential. In each MD simulation, a liquid film was initialized between vapor regions and NVE-type simulations were run to equilibrium. The simulation domain was divided into bins across the interfacial region for fluid density collection, and the resultant interfacial region density profile was used for surface tension evaluation. Application of the EFEDI method to these MD simulation results exhibited good approximations to surface tension as a function of temperature for both a simple and complex potential.

Interactions Between High-Viscosity Droplets Deposited on a Surface: Experiments and Simulations

2012 ◽  
Author(s):  
J. Esmaeelpanah ◽  
A. Dalili ◽  
S. Chandra ◽  
J. Mostaghimi ◽  
H. C. Fan ◽  
...  
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Piecewise Linear ◽  
Three Dimensional ◽  
Surface Force ◽  
Line Length ◽  
High Viscosity ◽  
Droplet Shape ◽  
Viscous Liquids ◽  
Straight Lines

A combined numerical and experimental investigation of coalescence of droplets of highly viscous liquids dropped on a surface has been carried out. Droplets of 87 wt% glycerin-in-water solutions with viscosity 110 centistokes were deposited sequentially in straight lines onto a flat, solid steel plate and droplet impact photographed. Impacting droplets spread on the surface until liquid surface tension and viscosity overcame inertial forces and the droplets recoiled, eventually reaching equilibrium. Droplet center-to-center distance was varied and droplet line length was measured from photographs. As droplet spacing was increased there was less interaction between the droplets. A three dimensional parallel code has been developed to simulate fluid flow and free surface interaction by solving the continuity, momentum and volume-of-fluid (VOF) equations. The two-step projection method was employed to solve the governing equations for the whole domain including both liquid and air phases. The continuum-surface-force (CSF) scheme was applied to model surface tension and the piecewise-linear-interface-construction (PLIC) technique used to reconstruct the free surface. Computer generated images of impacting droplets modeled droplet shape evolution correctly and compared well with photographs taken during experiments. Accurate predictions were obtained for droplet line length during spreading and at equilibrium.

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