10 research outputs found
Simplex space-time meshes in thermally coupled two-phase flow simulations of mold filling
The quality of plastic parts produced through injection molding depends on
many factors. Especially during the filling stage, defects such as weld lines,
burrs, or insufficient filling can occur. Numerical methods need to be employed
to improve product quality by means of predicting and simulating the injection
molding process. In the current work, a highly viscous incompressible
non-isothermal two-phase flow is simulated, which takes place during the cavity
filling. The injected melt exhibits a shear-thinning behavior, which is
described by the Carreau-WLF model. Besides that, a novel discretization method
is used in the context of 4D simplex space-time grids [2]. This method allows
for local temporal refinement in the vicinity of, e.g., the evolving front of
the melt [10]. Utilizing such an adaptive refinement can lead to locally
improved numerical accuracy while maintaining the highest possible
computational efficiency in the remaining of the domain. For demonstration
purposes, a set of 2D and 3D benchmark cases, that involve the filling of
various cavities with a distributor, are presented.Comment: 14 pages, 11 Figures, 4 Table
A Robin-Neumann Scheme with Quasi-Newton Acceleration for Partitioned Fluid-Structure Interaction
The Dirichlet-Neumann scheme is the most common partitioned algorithm for
fluid-structure interaction (FSI) and offers high flexibility concerning the
solvers employed for the two subproblems. Nevertheless, it is not without
shortcomings: To begin with, the inherent added-mass effect often destabilizes
the numerical solution severely. Moreover, the Dirichlet-Neumann scheme cannot
be applied to FSI problems in which an incompressible fluid is fully enclosed
by Dirichlet boundaries, as it is incapable of satisfying the volume
constraint. In the last decade, interface quasi-Newton methods have proven to
control the added-mass effect and substantially speed up convergence by adding
a Newton-like update step to the Dirichlet-Neumann coupling. They are, however,
without effect on the incompressibility dilemma. As an alternative, the
Robin-Neumann scheme generalizes the fluid's boundary condition to a Robin
condition by including the Cauchy stresses. While this modification in fact
successfully tackles both drawbacks of the Dirichlet-Neumann approach, the
price to be paid is a strong dependency on the Robin weighting parameter, with
very limited a priori knowledge about good choices. This work proposes a
strategy to merge these two ideas and benefit from their combined strengths.
The effectiveness of this new quasi-Newton-accelerated Robin-Neumann scheme is
demonstrated for different FSI simulations and compared to both Robin- and
Dirichlet-Neumann variants.Comment: Keywords: Partitioned Fluid-Structure Interaction, Robin-Neumann
Scheme,Interface Quasi-Newton Method
What does it mean to say that economics is performative?â Forthcoming in
Centre de Sociologie de lâInnovation Ecole des Mines de Pari
Treatable traits in the NOVELTY study
CorrigendumVolume 27, Issue 12, Respirology, pages: 1095-1095. First Published online: November 6, 2022 10.1111/resp.14406International audienceAsthma and chronic obstructive pulmonary disease (COPD) are two prevalent and complex diseases that require personalized management. Although a strategy based on treatable traits (TTs) has been proposed, the prevalence and relationship of TTs to the diagnostic label and disease severity established by the attending physician in a real-world setting are unknown. We assessed how the presence/absence of specific TTs relate to the diagnosis and severity of 'asthma', 'COPD' or 'asthmaâ+âCOPD'
Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo
International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100â105âMâ, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass âŒ150âMâ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200âMâ and effective aligned spin 0.8 at 0.056 Gpcâ3 yrâ1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpcâ3 yrâ1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]â Deceased, August 2020