1,909 research outputs found
Modelling of the moving deformed triple contact line: influence of the fluid inertia
For partial wetting, motion of the triple liquid-gas-solid contact line is
influenced by heterogeneities of the solid surface. This influence can be
strong in the case of inertial (e.g. oscillation) flows where the line can be
pinned or move intermittently. A model that takes into account both surface
defects and fluid inertia is proposed. The viscous dissipation in the bulk of
the fluid is assumed to be negligible as compared to the dissipation in the
vicinity of the contact line. The equations of motion and the boundary
condition at the contact line are derived from Hamilton's principle. The rapid
capillary rise along a vertical inhomogeneous wall is treated as an example.Comment: 19 pages and 3 figure
Experimental evidence of shock mitigation in a Hertzian tapered chain
We present an experimental study of the mechanical impulse propagation
through a horizontal alignment of elastic spheres of progressively decreasing
diameter , namely a tapered chain. Experimentally, the diameters of
spheres which interact via the Hertz potential are selected to keep as close as
possible to an exponential decrease, , where the
experimental tapering factor is either ~% or ~%.
In agreement with recent numerical results, an impulse initiated in a
monodisperse chain (a chain of identical beads) propagates without shape
changes, and progressively transfer its energy and momentum to a propagating
tail when it further travels in a tapered chain. As a result, the front pulse
of this wave decreases in amplitude and accelerates. Both effects are
satisfactorily described by the hard spheres approximation, and basically, the
shock mitigation is due to partial transmissions, from one bead to the next, of
momentum and energy of the front pulse. In addition when small dissipation is
included, a better agreement with experiments is found. A close analysis of the
loading part of the experimental pulses demonstrates that the front wave adopts
itself a self similar solution as it propagates in the tapered chain. Finally,
our results corroborate the capability of these chains to thermalize
propagating impulses and thereby act as shock absorbing devices.Comment: ReVTeX, 7 pages with 6 eps, accepted for Phys. Rev. E (Related papers
on http://www.supmeca.fr/perso/jobs/
Toward a Universal Model of Breaking Waves on Shallow Water
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive
Unsteady undular bores in fully nonlinear shallow-water theory
We consider unsteady undular bores for a pair of coupled equations of
Boussinesq-type which contain the familiar fully nonlinear dissipationless
shallow-water dynamics and the leading-order fully nonlinear dispersive terms.
This system contains one horizontal space dimension and time and can be
systematically derived from the full Euler equations for irrotational flows
with a free surface using a standard long-wave asymptotic expansion.
In this context the system was first derived by Su and Gardner. It coincides
with the one-dimensional flat-bottom reduction of the Green-Naghdi system and,
additionally, has recently found a number of fluid dynamics applications other
than the present context of shallow-water gravity waves. We then use the
Whitham modulation theory for a one-phase periodic travelling wave to obtain an
asymptotic analytical description of an undular bore in the Su-Gardner system
for a full range of "depth" ratios across the bore. The positions of the
leading and trailing edges of the undular bore and the amplitude of the leading
solitary wave of the bore are found as functions of this "depth ratio". The
formation of a partial undular bore with a rapidly-varying finite-amplitude
trailing wave front is predicted for ``depth ratios'' across the bore exceeding
1.43. The analytical results from the modulation theory are shown to be in
excellent agreement with full numerical solutions for the development of an
undular bore in the Su-Gardner system.Comment: Revised version accepted for publication in Phys. Fluids, 51 pages, 9
figure
THE DIRECTIONS OF MODERNIZATION OF THE SYSTEM’S INTEGRATION TECHNOLOGIES IN THE PEDAGOGICS: MODELS CREATION STAGES
В статье рассматриваются возможности использования методологии системной интеграции в качестве элемента педагогической интеграцииThe article describes the possibilities of using the methodology of the system’s integration technologies as an element of pedagogical integratio
A unified hyperbolic formulation for viscous fluids and elastoplastic solids
We discuss a unified flow theory which in a single system of hyperbolic
partial differential equations (PDEs) can describe the two main branches of
continuum mechanics, fluid dynamics, and solid dynamics. The fundamental
difference from the classical continuum models, such as the Navier-Stokes for
example, is that the finite length scale of the continuum particles is not
ignored but kept in the model in order to semi-explicitly describe the essence
of any flows, that is the process of continuum particles rearrangements. To
allow the continuum particle rearrangements, we admit the deformability of
particle which is described by the distortion field. The ability of media to
flow is characterized by the strain dissipation time which is a characteristic
time necessary for a continuum particle to rearrange with one of its
neighboring particles. It is shown that the continuum particle length scale is
intimately connected with the dissipation time. The governing equations are
represented by a system of first order hyperbolic PDEs with source terms
modeling the dissipation due to particle rearrangements. Numerical examples
justifying the reliability of the proposed approach are demonstrated.Comment: 6 figure
Tunability of solitary wave properties in one dimensional strongly nonlinear phononic crystals
One dimentional strongly nonlinear phononic crystals were assembled from
chains of PTFE (polytetrafluoroethylene) and stainless steel spheres with
gauges installed inside the beads. Trains of strongly nonlinear solitary waves
were excited by an impact. A significant modification of the signal shape and
an increase of solitary wave speed up to two times (at the same amplitude of
dynamic contact force)were achieved through a noncontact magnetically induced
precompression of the chains. Data for PTFE based chains are presented for the
first time and data for stainless steel based chains were extended into a
smaller range of amplitudes by more than one order of magnitude than previously
reported. Experimental results were found to be in reasonable agreement with
the long wave approximation and with numerical calculations based on Hertz
interaction law for discrete chains.Comment: 36 pages, 7 figure
Magnetoelectric ordering of BiFeO3 from the perspective of crystal chemistry
In this paper we examine the role of crystal chemistry factors in creating
conditions for formation of magnetoelectric ordering in BiFeO3. It is generally
accepted that the main reason of the ferroelectric distortion in BiFeO3 is
concerned with a stereochemical activity of the Bi lone pair. However, the lone
pair is stereochemically active in the paraelectric orthorhombic beta-phase as
well. We demonstrate that a crucial role in emerging of phase transitions of
the metal-insulator, paraelectric-ferroelectric and magnetic disorder-order
types belongs to the change of the degree of the lone pair stereochemical
activity - its consecutive increase with the temperature decrease. Using the
structural data, we calculated the sign and strength of magnetic couplings in
BiFeO3 in the range from 945 C down to 25 C and found the couplings, which
undergo the antiferromagnetic-ferromagnetic transition with the temperature
decrease and give rise to the antiferromagnetic ordering and its delay in
regard to temperature, as compared to the ferroelectric ordering. We discuss
the reasons of emerging of the spatially modulated spin structure and its
suppression by doping with La3+.Comment: 18 pages, 5 figures, 3 table
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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