164,677 research outputs found
A Three-dimensional Numerical Model for Baroclinic Dynamic in the Malacca Strait
The circulation in the Malacca Strait is simulated using a three-dimensionalbaroclinic numerical model. The circulation model isderived from the combined effects of tides, wind, meteorologicalforcings, temperature and salinity. The computational results producedpattern of general circulation and also sea surface temperature andsalinity. In the present study, the pattem of current circulation in theMalacca Strait coincided with the work [7]
A numerical model of the VKS experiment
We present numerical simulations of the magnetic field generated by the flow
of liquid sodium driven by two counter-rotating impellers (VKS experiment).
Using a dynamo kinematic code in cylindrical geometry, it is shown that
different magnetic modes can be generated depending on the flow configuration.
While the time averaged axisymmetric mean flow generates an equatorial dipole,
our simulations show that an axial field of either dipolar or quadrupolar
symmetry can be generated by taking into account non-axisymmetric components of
the flow. Moreover, we show that by breaking a symmetry of the flow, the
magnetic field becomes oscillatory. This leads to reversals of the axial dipole
polarity, involving a competition with the quadrupolar component.Comment: 6 pages, 5 figure
A numerical model for multigroup radiation hydrodynamics
We present in this paper a multigroup model for radiation hydrodynamics to
account for variations of the gas opacity as a function of frequency. The
entropy closure model (M1) is applied to multigroup radiation transfer in a
radiation hydrodynamics code. In difference from the previous grey model, we
are able to reproduce the crucial effects of frequency-variable gas opacities,
a situation omnipresent in physics and astrophysics. We also account for the
energy exchange between neighbouring groups which is important in flows with
strong velocity divergence. These terms were computed using a finite volume
method in the frequency domain. The radiative transfer aspect of the method was
first tested separately for global consistency (reversion to grey model) and
against a well established kinetic model through Marshak wave tests with
frequency dependent opacities. Very good agreement between the multigroup M1
and kinetic models was observed in all tests. The successful coupling of the
multigroup radiative transfer to the hydrodynamics was then confirmed through a
second series of tests. Finally, the model was linked to a database of
opacities for a Xe gas in order to simulate realistic multigroup radiative
shocks in Xe. The differences with the previous grey models are discussed.Comment: 27 pages, 11 figures, Accepted for publication in JQSR
Numerical model for granular compaction under vertical tapping
A simple numerical model is used to simulate the effect of vertical taps on a
packing of monodisperse hard spheres. Our results are in agreement with an
experimantal work done in Chicago and with other previous models, especially
concerning the dynamics of the compaction, the influence of the excitation
strength on the compaction efficiency, and some ageing effects. The principal
asset of the model is that it allows a local analysis of the packings. Vertical
and transverse density profiles are used as well as size and volume
distributions of the pores. An interesting result concerns the appearance of a
vertical gradient in the density profiles during compaction. Furthermore, the
volume distribution of the pores suggests that the smallest pores, ranging in
size between a tetrahedral and an octahedral site, are not strongly affected by
the tapping process, in contrast to the largest pores which are more sensitive
to the compaction of the packing.Comment: 8 pages, 15 figures (eps), to be published in Phys. Rev. E. Some
corrections have been made, especially in paragraph IV
A numerical model of standard to blowout jets
We report on three-dimensional (3D) MHD simulations of the formation of jets produced during the emergence and eruption of solar magnetic fields. The interaction between an emerging and an ambient magnetic field in the solar atmosphere leads to (external) reconnection and the formation of "standard" jets with an inverse Y-shaped configuration. Eventually, low-atmosphere (internal) reconnection of sheared fieldlines in the emerging flux region produces an erupting magnetic flux rope and a reconnection jet underneath it. The erupting plasma blows out the ambient field and, moreover, it unwinds as it is ejected into the outer solar atmosphere. The fast emission of the cool material that erupts together with the hot outflows due to external/internal reconnection form a wider "blowout" jet. We show the transition from "standard" to "blowout" jets and report on their 3D structure. The physical plasma properties of the jets are consistent with observational studies.Peer reviewe
Numerical model for material parameter identification of cells
Bacteria have a complex external layer that render them with an increased stiffness and more resistant to external invasion. The works aims to model the squeezing of a bacteria between two walls, and deduce the composition of bacterial external layer from the observed deformations. A FE based model will be developed for inferring the stiffness of baceria, solving an inverse problem from the applied loading and measured displacements. The results will be applied to laboraotry experiments carried out at Institu of Bioengineering of Catalunya (IBEC)
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