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BEGIN:VEVENT
SUMMARY:On some models for bifluid flows
DTSTART;VALUE=DATE-TIME:20151106T080000Z
DTEND;VALUE=DATE-TIME:20151106T084500Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2229@indico.math.cnrs.fr
DESCRIPTION:Speakers: Didier BRESCH (Université de Savoie)\nIn this talk
I will discuss some low Mach number systems for bifluid flows. More precis
ely I will focus on mathematical structures for systems used for bilayer s
hallow-water flows in a fixed channel or incompressible bifluid models and
mixture systems used for instance for pollutant spreading or aerated aval
anches (miscible flows). \n\nThis corresponds respectively to joint works
with M. Renardy and with V. Giovangigli\, E. Zatorska.\n\nhttps://indico.m
ath.cnrs.fr/event/601/contributions/2229/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2229/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Asymptotic limits of the Shallow Water equations
DTSTART;VALUE=DATE-TIME:20151106T150000Z
DTEND;VALUE=DATE-TIME:20151106T154500Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2228@indico.math.cnrs.fr
DESCRIPTION:Speakers: Carine Lucas (MAPMO\, Université d'Orléans)\nIn th
is talk\, I will explain the asymptotic limits that can be obtained from t
he Shallow Water equations. \nIn the Shallow Water equations\, the values
of two non-dimensional numbers (the Strouhal and the Froude numbers) can b
e chosen in order to catch various physical phenomena. We will see that\,
depending on the links between the Strouhal number\, the Froude number\,
and the scales of the topography\, we get other well-known equations such
as the "Lake equation" for example. \n\nThis work has been done in collabo
ration with Didier Bresch (LAMA\, Université de Savoie\, France) and Rupe
rt Klein (Free University of Berlin\, Germany).\n\nhttps://indico.math.cnr
s.fr/event/601/contributions/2228/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2228/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Session poster
DTSTART;VALUE=DATE-TIME:20151106T084500Z
DTEND;VALUE=DATE-TIME:20151106T093000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2227@indico.math.cnrs.fr
DESCRIPTION:https://indico.math.cnrs.fr/event/601/contributions/2227/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2227/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A low Mach correction for the Godunov scheme applied to the linear
wave equation with porosity
DTSTART;VALUE=DATE-TIME:20151105T154500Z
DTEND;VALUE=DATE-TIME:20151105T163000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2226@indico.math.cnrs.fr
DESCRIPTION:Speakers: Jonathan Jung (EFREI)\nWe study the low Mach number
behavior of the Godunov finite volume scheme applied to\nthe linear wave e
quation with porosity. More precisely\, we extend the Hodge decomposition
to\na weighted L^2 space. We illustrate the influence of the cell geometry
on the accuracy property at low Mach number. In the triangular case\, the
stationary space of the Godunov scheme approaches well enough the continu
ous space of constant pressure and divergent-free velocity while this is n
ot the case in the cartesian case. We study the properties of the modified
equation associated to this Godunov scheme and we propose some correction
that is continuous with respect to the Mach number.\n\nhttps://indico.mat
h.cnrs.fr/event/601/contributions/2226/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2226/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Low-velocity scheme for hyperbolic conservation laws with constrai
ns
DTSTART;VALUE=DATE-TIME:20151106T104500Z
DTEND;VALUE=DATE-TIME:20151106T113000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2225@indico.math.cnrs.fr
DESCRIPTION:Speakers: Martin Parisot (ANGE\, Inria Paris Rocquencourt)\nTh
is talk is devoted to the numerical approximation of first order conservat
ion laws under constraints.\nThe proposed strategy is based on a relaxatio
n of the constraints in order to get a system of hyperbolic conservation l
aws.\nHowever\, the new system have to be considerate at the limit of the
relaxation parameter goes to zero to ensure the (formal) consistency with
the initial model.\nWe will explain how this limit is analogous to a low-M
ach asymptotic and we will propose several examples and illustrations.\n\n
https://indico.math.cnrs.fr/event/601/contributions/2225/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2225/
END:VEVENT
BEGIN:VEVENT
SUMMARY:CDMATH library and low-Mach models applied to two-phase flows with
Adaptive Mesh Refinement
DTSTART;VALUE=DATE-TIME:20151105T134500Z
DTEND;VALUE=DATE-TIME:20151105T143000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2224@indico.math.cnrs.fr
DESCRIPTION:Speakers: Anouar Mekkas (DEN/DANS/DM2S\, CEA SAclay)\, Arthur
Talpaert (DEN/DANS/DM2S\, CEA Saclay & CMAP)\nThis work presents the incre
mental implementation of the simulation of two-phase flows in low-Mach con
ditions\, particularly for dilating bubbles in a nuclear core. We use CDMA
TH\, a new easy-to-use and open-source library\, which relies on the rich
MED Coupling library for powerful visualization. We provide simple tools f
or patch-based Adaptive Mesh Refinement (AMR) designed with parallel and b
alanced computing in mind. With AMR\, we refined the coarse mesh on a set
of patches in order to locally improve the precision in regions of interes
t and such that we finely capture changes located at the interface. The mo
dels we present are simplified but necessary steps to obtain efficient sim
ulation of the incompressible Navier-Stokes model and of the low Mach mode
l with interface.\n\nThis research is a joint work together with Grégoire
Allaire\, Stéphane Dellacherie and Samuel Kokh. It is sponsored by the C
EA (French Atomic Energy Commission) and the DGA (French ministry of defen
se).\n\nhttps://indico.math.cnrs.fr/event/601/contributions/2224/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2224/
END:VEVENT
BEGIN:VEVENT
SUMMARY:An all-regime Lagrange-Projection like scheme for 2D homogeneous m
odels for two-phase flows on unstructured meshes
DTSTART;VALUE=DATE-TIME:20151106T100000Z
DTEND;VALUE=DATE-TIME:20151106T104500Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2223@indico.math.cnrs.fr
DESCRIPTION:Speakers: Mathieu Girardin (CMAP\, Ecole Polytechnique)\nWe pr
opose an all regime Lagrange-Projection like numerical scheme for 2D homog
eneous models for two-phase flows. By all regime\, we mean that the numeri
cal scheme is able to compute accurate approximate solutions with an under
-resolved discretization\, i.e. a mesh size and time step much bigger than
the Mach number M of the mixture. \n\nThe key idea is to decouple acousti
c\, transport and phase transition phenomenon using a Lagrange-Projection
decomposition in order to treat implicitly (fast) acoustic and phase trans
ition phenomenon and explicitly the (slow) transport phenomena. Then\, ext
ending a strategy developed in the case of the usual gas dynamics equation
s\, we alter the numerical flux in the acoustic approximation to obtain an
uniform truncation error in term of M. This modified scheme is conservati
ve and endowed with good stability properties with respect to the positivi
ty of the density and preserving the mass fraction within the interval (0\
,1). \n\nNumerical evidences are proposed and show the ability of the sche
me to deal with tests where the flow regime may vary from low to high Mach
values.\n\nhttps://indico.math.cnrs.fr/event/601/contributions/2223/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2223/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Low Mach number flow in plate-type fuel cores
DTSTART;VALUE=DATE-TIME:20151105T100000Z
DTEND;VALUE=DATE-TIME:20151105T104500Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2222@indico.math.cnrs.fr
DESCRIPTION:Speakers: Anne Charmeau (DEN/DANS/DM2S\, CEA Saclay)\nhttps://
indico.math.cnrs.fr/event/601/contributions/2222/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2222/
END:VEVENT
BEGIN:VEVENT
SUMMARY:High temperature thermalhydraulics modeling of a Molten salt: appl
ication to the molten salt nuclear reactor
DTSTART;VALUE=DATE-TIME:20151105T104500Z
DTEND;VALUE=DATE-TIME:20151105T113000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2221@indico.math.cnrs.fr
DESCRIPTION:Speakers: Pablo Rubiolo (IN2P3\, CNRS Grenoble)\nAn overview o
f the ongoing efforts in the area of the thermal-hydraulics modeling of a
Molten Salt Fast Reactor (MSFR) is presented. The MFSR employs a flowing l
iquid fuel based on a high temperature lithium fluoride salt. A molten fue
l salt flow can be considered in many situations as an incompressible flow
(low Match). However\, several phenomena intrinsic to a molten fuel salt
flow posse unique challenges (radiative heat transfer\, volumetric heat so
urce\, phase change\, strong neutronics feedbacks\, etc.). To study some o
f these phenomena and to improve current CFD models an experimental facili
ty called SWATH (Salt at WAll: Thermal ExcHanges) will be built as part of
the European project SAMOFAR (2015-2019).\n\nhttps://indico.math.cnrs.fr/
event/601/contributions/2221/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2221/
END:VEVENT
BEGIN:VEVENT
SUMMARY:An Asymptotic Preserving scheme in the low-Mach number limit for t
he Euler system
DTSTART;VALUE=DATE-TIME:20151105T150000Z
DTEND;VALUE=DATE-TIME:20151105T154500Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2220@indico.math.cnrs.fr
DESCRIPTION:Speakers: Marie-Hélène Vignal (IMT\, Université Toulouse 3)
\nI am interested in the so-called Asymptotic preserving schemes. These sc
hemes are well known to be well adapted for the resolution of multiscale p
roblems in which several regimes are present. I will present the particula
r case of the low Mach number limit for the Euler system. We recall that w
hen the Mach number tends to zero\, the pressure waves are very fast and t
his yields the fluid incompressible. When a standard explicit finite volum
e scheme is used\, it is well known that its time step is constrained by t
he C.F.L. (Courant-Friedrichs\, Levy) condition. In the low Mach number re
gime\, this leads to time steps invertely proportional to the very large p
ressure waves velocity. Thus\, explicit schemes suffer from a severe numer
ical constraint in low-Mach regimes. Furthermore\, these schemes are not c
onsistent in this regime. This means that they do not capture the incompre
ssible limit even if they are used with constrained meshes. Then\, it is n
ecessary to develop new schemes for bypassing these limitations. These new
schemes must be stable and consistent in all regimes: from low Mach numbe
rs to order one Mach numbers.\n\nI will show how to construct such a schem
e for the Euler system and I will present numerical\nresults showing the g
ood behavior of these schemes in all regimes.\n\nhttps://indico.math.cnrs.
fr/event/601/contributions/2220/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2220/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Low Mach Number Modeling of Stratified Astrophysical Flows
DTSTART;VALUE=DATE-TIME:20151106T130000Z
DTEND;VALUE=DATE-TIME:20151106T134500Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2219@indico.math.cnrs.fr
DESCRIPTION:Speakers: Ann Almgren (Lawrence Berkeley Lab\, USA)\nComputati
onal astrophysics has traditionally relied on discretizations of\neither t
he fully compressible equations for fluid dynamics\, or the\nanelastic ap
proximation\, supplemented by equations describing the\nthermonuclear reac
tions and heat release. The low Mach number formulation\,\nlike the anela
stic approximation\, analytically removes acoustic wave propagation\nfrom
the system. However\, the more general low Mach number approach\nretains
nonlinear compressibility effects resulting from nuclear burning\,\ncompos
itional changes and changing radial stratification. This model\nis a gene
ralization of the pseudo-incompressible approximation\nto systems with a n
on-ideal gas equation of state and a time-varying base state.\nI will disc
uss the derivation of the low Mach number equation set for\nastrophysics\,
focusing on the similarities with and differences from\nnumerical models
of the Earth's atmosphere.\n\nhttps://indico.math.cnrs.fr/event/601/contri
butions/2219/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2219/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mathematical analysis of low Mach number flows for some single and
two phase models
DTSTART;VALUE=DATE-TIME:20151105T084500Z
DTEND;VALUE=DATE-TIME:20151105T093000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2218@indico.math.cnrs.fr
DESCRIPTION:Speakers: Benoit Desjardins (FMJH)\nThere has been a lot of pr
ogress in the last 10 years for the mathematical analysis of low Mach numb
er flows in the case of single phase flows. Similar questions can be raise
d in the two phase framework\, where one or the two phases are slightly co
mpressible: this talk presents some of the additional difficulties of low
Mach number analysis for two phase compressible models\, which are widely
used in industrial applications. Only one pressure four equations models w
ill be considered (no temperature equations).\n\nhttps://indico.math.cnrs.
fr/event/601/contributions/2218/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2218/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Turbulent kinetic energy transfers in low-Mach wall-bounded flows
DTSTART;VALUE=DATE-TIME:20151106T134500Z
DTEND;VALUE=DATE-TIME:20151106T143000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2217@indico.math.cnrs.fr
DESCRIPTION:Speakers: Adrien Toutant (PROMES\, Université de Perpignan)\n
The context of the study is high temperature solar receivers (SR). The mai
n characteristics of flow inside a SR are turbulence (because flow rates a
re important) and temperature gradient (because only one face of the SR re
ceives concentrated sunlight). A specific algorithm for the resolution of
low-Mach equations is proposed in order to improve mass and energy conserv
ations. Direct numerical simulations (DNS) of a simplified solar receiver
in a bi-periodic plane channel are carried out in order to analyze the cou
pling between turbulence and temperature gradients. \n\nThe results show t
hat the temperature gradient creates asymmetric profiles of mean and fluct
uating velocities. This asymmetry cannot only be explained by the fluid pr
operty variations as a function of temperature. It is truly related to the
coupling of velocity / temperature\, which mainly leads to an increase of
the turbulent intensity at the cold side and to its decrease at the hot s
ide. The analysis of the turbulent kinetic energy in the physical and in t
he spectral domains shows that temperature gradient changes the mechanisms
of production\, transfer and dissipation.\n\nhttps://indico.math.cnrs.fr/
event/601/contributions/2217/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2217/
END:VEVENT
BEGIN:VEVENT
SUMMARY:On the stability of IMEX schemes for singular hyperbolic PDE's
DTSTART;VALUE=DATE-TIME:20151105T130000Z
DTEND;VALUE=DATE-TIME:20151105T134500Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2215@indico.math.cnrs.fr
DESCRIPTION:Speakers: Sebastian Noelle (RWTH Aachen\, Germany)\nI will dis
cuss systems of conservation laws where some wave speeds become singular.
The classic example is the low Mach number limit in gas dynamics. In the s
ingular limit\, hyperbolicity gets lost\, and near the limit\, explicit t
ime discretizations become either inefficient or unstable\, both due to th
e CFL condition. The established concept to design efficient and stable al
gorithms near the singular limit is a time-Implicit-Explicit splitting\,
called IMEX. The recent asymptotic preserving (AP) IMEX schemes are consis
tent with the singular limit. A key question is the asymptotic stability o
f these schemes. I discuss two examples: a well-known\, but unstable\, sch
eme\, and an also well-known\, but stable scheme. Then I present a new sta
bility analysis for IMEX schemes\, which explains the outcomes of these ex
periments. I also give an outlook to a new concept of splittings\, the so
called RS-IMEX schemes (Reference Solution IMEX)\, and first aplications.
\n\nhttps://indico.math.cnrs.fr/event/601/contributions/2215/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2215/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Godunov type schemes for low Froude flows with Coriolis force
DTSTART;VALUE=DATE-TIME:20151106T154500Z
DTEND;VALUE=DATE-TIME:20151106T163000Z
DTSTAMP;VALUE=DATE-TIME:20200807T162830Z
UID:indico-contribution-601-2214@indico.math.cnrs.fr
DESCRIPTION:Speakers: Emmanuel Audusse (LAGA\, Université Paris 13)\nin t
his talk\, we are interested in the numerical simulation of free surface g
eophysical flows. Our objective is to study the relation between two well
known categories of numerical schemes: the well-balanced schemes that are
designed to preserve some stationary states of the model and the low Froud
e number schemes that are designed to remain accurate in some asymptotic r
egime. We study two particular cases that are related to the presence of t
opography and Coriolis source terms. More particularly we analyze the line
arized system in order to identify the kernel of the associated operator a
nd to derive stable and accurate numerical schemes.\n\nhttps://indico.math
.cnrs.fr/event/601/contributions/2214/
LOCATION:Université Paris Descartes Amphi Lavoisier A\, 3rd floor
URL:https://indico.math.cnrs.fr/event/601/contributions/2214/
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