2,689 research outputs found
Histogram analysis as a method for determining the line tension by Monte-Carlo simulations
A method is proposed for determining the line tension, which is the main
physical characteristic of a three-phase contact region, by Monte-Carlo (MC)
simulations. The key idea of the proposed method is that if a three-phase
equilibrium involves a three-phase contact region, the probability distribution
of states of a system as a function of two order parameters depends not only on
the surface tension, but also on the line tension. This probability
distribution can be obtained as a normalized histogram by appropriate MC
simulations, so one can use the combination of histogram analysis and
finite-size scaling to study the properties of a three phase contact region.
Every histogram and results extracted therefrom will depend on the size of the
simulated system. Carrying out MC simulations for a series of system sizes and
extrapolating the results, obtained from the corresponding series of
histograms, to infinite size, one can determine the line tension of the three
phase contact region and the interfacial tensions of all three interfaces (and
hence the contact angles) in an infinite system. To illustrate the proposed
method, it is applied to the three-dimensional ternary fluid mixture, in which
molecular pairs of like species do not interact whereas those of unlike species
interact as hard spheres. The simulated results are in agreement with
expectations
An Equation of State of Gases at High Temperatures and Densities
State equation of molecular gas at high temperatures and densitie
Formation of capillary bridges in AFM-like geometry
We discuss the phase diagram of fluid confined in AFM-like geometry. It
combines the properties of capillary condensation and complete filling of a
wedge.Comment: 9 pages, 7 figure
Stability of freely falling granular streams
A freely falling stream of weakly cohesive granular particles is modeled and
analysed with help of event driven simulations and continuum hydrodynamics. The
former show a breakup of the stream into droplets, whose size is measured as a
function of cohesive energy. Extensional flow is an exact solution of the
one-dimensional Navier-Stokes equation, corresponding to a strain rate,
decaying like 1/t from its initial value, gammaDot0. Expanding around this
basic state, we show that the flow is stable for short times (gammaDot0 * t <<
1), whereas for long times (gammaDot0 * t >> 1) perturbations of all wavelength
grow. The growthrate of a given wavelength depends on the instant of time when
the fluctuation occurs, so that the observable patterns can vary considerably.Comment: 4 page, 5 figures. Submitted to PRL. Supplementary material: see
http://wwwuser.gwdg.de/~sulrich/research/#Publication
The influence of line tension on the formation of liquid bridges
The formation of liquid bridges between a planar and conical substrates is
analyzed macroscopically taking into account the line tension. Depending on the
value of the line tension coefficient \tau and geometric parameters of the
system one observes two different scenarios of liquid bridge formation upon
changing the fluid state along the bulk liquid-vapor coexistence. For \tau >
\tau * (\tau * < 0) there is a first-order transition to a state with
infinitely thick liquid bridge. For \tau < \tau * the scenario consists of two
steps: first there is a first-order transition to a state with liquid bridge of
finite thickness which upon further increase of temperature is followed by
continuous growth of the thickness of the bridge to infinity. In addition to
constructing the relevant phase diagram we examine the dependence of the width
of the bridge on thermodynamic and geometric parameters of the system.Comment: 4 pages, 5 figure
Reply to Comment on: "Are stress-free membranes really 'tensionless'?"
This is a reply to a comment on the paper arXiv:1204.2075 "Are stress-free
membranes really tensionless ?" (EPL 95,28008 (2011))
Are stress-free membranes really 'tensionless'?
In recent years it has been argued that the tension parameter driving the
fluctuations of fluid membranes, differs from the imposed lateral stress, the
'frame tension'. In particular, stress-free membranes were predicted to have a
residual fluctuation tension. In the present paper, this argument is
reconsidered and shown to be inherently inconsistent -- in the sense that a
linearized theory, the Monge model, is used to predict a nonlinear effect.
Furthermore, numerical simulations of one-dimensional stiff membranes are
presented which clearly demonstrate, first, that the internal 'intrinsic'
stress in membranes indeed differs from the frame tension as conjectured, but
second, that the fluctuations are nevertheless driven by the frame tension.
With this assumption, the predictions of the Monge model agree excellently with
the simulation data for stiffness and tension values spanning several orders of
magnitude
Surface tension of electrolytes: Hydrophilic and hydrophobic ions near an interface
We calculate the ion distributions around an interface in fluid mixtures of
highly polar and less polar fluids (water and oil) for two and three ion
species. We take into account the solvation and image interactions between ions
and solvent. We show that hydrophilic and hydrophobic ions tend to undergo a
microphase separation at an interface, giving rise to an enlarged electric
double layer. We also derive a general expression for the surface tension of
electrolyte systems, which contains a negative electrostatic contribution
proportional to the square root of the bulk salt density. The amplitude of this
square-root term is small for hydrophilic ion pairs, but is much increased for
hydrophilic and hydrophobic ion pairs. For three ion species including
hydrophilic and hydrophobic ions, we calculate the ion distributions to explain
those obtained by x-ray reflectivity measurements.Comment: 8 figure
Design the "Building in Construction" for the progress-users: a 4D perspective
The implementation of Building Information Modeling (BIM) is driving and enabling a paradigm shift in building design methods. Traditional architectural design process focuses on the design of “form, space and order” of the built environment, responding to the need and demand of the clients, the “end-users”. Under this professional paradigm, construction workers, the builders, are part of the construction machine to turn the design into reality. However, the “building in construction” is the working environment of builders, in which they spend most of their time in their everyday lives. They are “progress-users” of the building environment, a changing environment composed of building components, scaffolds, moving equipment and temporary facilities. They are performing various activities, which has a great impact on their physical and psychological health, and more importantly, their safety. If we add the time dimension into the building process, the concept of “user” needs to be extended and the dynamic environment needs to be taken into account at the stage of architectural design. This paper argues for an alternative perspective on the built environment and proposes a methodology for sustainable architectural design through the implementation of BIM.postprin
Wetting on Nanorough Surfaces
We present in this Letter a free-energy approach to the dynamics of a fluid
near a nanostructured surface. The model accounts both for the static phase
equilibrium in the vicinity of the surface (wetting angles, Cassie-Wenzel
transition) and the dynamical properties like liquid slippage at the boundary.
This method bridges the gap between phenomenological phase-field approaches and
more macroscopic lattice-Boltzmann models
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