In this article, we present an immersed boundary method for the simulation of compressible flows of complex geometries encountered in aerodynamics. The immersed boundary methods allow the mesh not to ...conform to obstacles, whose influence is taken into account by modifying the governing equations locally (either by a source term within the equation or by imposing the flow variables or fluxes locally, similarly to a boundary condition). A main feature of the approach which we propose is that it relies on structured Cartesian grids in combination with a dedicated HPC Cartesian solver, taking advantage of their low memory and CPU time requirements but also the automation of the mesh generation and adaptation. Turbulent flow simulations are performed by solving the Reynolds-averaged Navier–Stokes equations or by a Large-Eddy simulation approach, in combination with a wall function at high Reynolds number, to mitigate the cell count resulting from the isotropic nature of Cartesian cells. The objective of this paper is to demonstrate that this automatic workflow is fast and robust and enables to get quantitative aerodynamics results on geometrically complex configurations. Results obtained are in good agreement with classical body-fitted approaches but with a significant reduction of the time of the whole process, that is a day for RANS simulations, including the mesh generation.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Noble gases serve as unique tracers of the origin and evolution of Earth's volatile reservoirs owing to their inert nature and contribution from extinct and extant radioactivities. However, noble ...gases are low in abundance relative to many other elements, particularly in the Earth's mantle. Additionally, mantle-derived samples show large post-eruptive atmospheric contamination, rendering the determination of the primary mantle composition challenging. The sources of mantle krypton and xenon remain debated due to their partially resolvable excess, if any, relative to the atmosphere. Atmospheric noble gases also appear to be recycled into the mantle via subduction, progressively overprinting the initial mantle signature. Here we develop a new protocol to accumulate non-contaminated mantle-derived xenon, in particular the low abundant 124-126-128Xe. The results show the highest excesses in 124-126-128Xe ever measured in the mantle relative to the atmosphere and point toward a chondritic origin for mantle xenon. The fissiogenic isotopes 131-132-134-136Xe allow the onset of efficient xenon recycling in the mantle to be constrained at around 3 Gyr ago, implying that volatile recycling before 3 Ga would have been negligible.
Despite the influence of mantle carbon on melt formation and migration, global volatile budgets, and volcanic eruption styles, the carbon concentration in Earth's upper mantle remains highly debated, ...with estimates varying by more than an order of magnitude. The relationship between carbon and incompatible trace element (e.g., Nb, Ba) concentrations in rare, undegassed mid-ocean ridge basalts and melt inclusions provide primary constraints on upper mantle carbon content. Here we investigate whether the most volatile rich mid-ocean ridge basalts, termed ‘popping rocks’, represent undegassed magmas from the upper mantle and provide insight into upper mantle carbon inventory. We show that fourteen new popping rocks, collected in situ from the Mid-Atlantic Ridge rift valley near 14°N, contain highly variable CO2/Nb and CO2/Ba ratios despite similar mantle sources and extents of melting. We revise the original model for popping rock formation using seafloor observations, high-resolution bathymetry, vesicle size distributions, major and trace element geochemistry, and noble gas geochemistry. Highly variable volatile concentrations despite relatively homogeneous trace element ratios and low 4He/40Ar⁎ suggest that bubble accumulation affected these popping rocks. These results provide evidence for heterogeneity in the CO2/Ba ratio of the depleted mantle and indicate that mantle carbon concentrations are lower and less heterogeneous than previously estimated, which influences models for mantle melting and CO2 flux at mid-ocean ridges.
•Bubble accumulation influences CO2 concentrations in Mid-Atlantic Ridge popping rocks.•Mantle carbon concentrations are lower than previously suggested based on popping rock 2πD43.•Pre-accumulation CO2/Ba ratios (16–22) provide evidence for heterogeneity in the depleted mantle ratio.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The isotopic and elemental compositions of noble gases constitute a powerful tool to study volatile origin and evolution, due to their inertness, and can thus provide crucial information about the ...early stage of planetary formation. Two models are proposed to explain the light noble gas origin on Earth: the solar wind implantation model and the solar nebula gas dissolution model. However, noble gas measurements often show addition of air to the mantle-derived gas, which complicates the determination of mantle isotopic ratios. We analysed the noble gas isotopic compositions of single vesicles in samples from the Galápagos hotspot with laser ablation, in order to understand and remove this atmospheric component, as well as discriminate between the two scenarios. Based on the new high precision results and a new statistical approach, we show that the solar wind implantation model is more likely to explain the terrestrial He, Ne and Ar composition. This scenario could bring important constraints on the solar system environment during the early stage of planetary formation.
In the framework of the GOAHEAD European project, CFD simulations around a complete helicopter configuration have been performed by the different partners to validate their codes and to compare with ...a detailed experimental database. At ONERA, the simulation of such a complex configuration is still challenging in terms of efforts required in the pre-processing phase, and in terms of CPU time. This test-case has been in particular used to set up a pre-processing chain of tools, going from the meshes described in a CGNS tree to the calculation input. This chain including the Chimera assembly of the different components of the helicopter is described in this paper. The second part presents some results of one of the test-cases performed by ONERA in the project: the cruise/tail shake flight condition. The results are compared with the experiment data and also with pre-tests CFD computations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Based on a detailed sedimentological analysis of Lower Triassic continental deposits in the western Germanic sag Basin (i.e. the eastern part of the present-day Paris Basin: the 'Conglomérat basal', ...'Grès vosgien' and 'Conglomérat principal' Formations), three main depositional environments were identified: (i) braided rivers in an arid alluvial plain with some preserved aeolian dunes and very few floodplain deposits; (ii) marginal erg (i.e. braided rivers, aeolian dunes and aeolian sand-sheets); and (iii) playa lake (an ephemeral lake environment with fluvial and aeolian sediments). Most of the time, aeolian deposits in arid environments that are dominated by fluvial systems are poorly preserved and particular attention should be paid to any sedimentological marker of aridity, such as wind-worn pebbles (ventifacts), sand-drift surfaces and aeolian sand-sheets. In such arid continental environments, stratigraphic surfaces of allocyclic origin correspond to bounding surfaces of regional extension. Elementary stratigraphic cycles, i.e. the genetic units, have been identified for the three main continental environments: the fluvial type, fluvial-aeolian type and fluvial/playa lake type. At the time scale of tens to hundreds of thousands of years, these high-frequency cycles of climatic origin are controlled either by the groundwater level in the basin or by the fluvial siliciclastic sediment input supplied from the highland. Lower Triassic deposits from the Germanic Basin are preserved mostly in endoreic basins. The central part of the basin is arid but the rivers are supplied with water by precipitation falling on the remnants of the Hercynian (Variscan)-Appalachian Mountains. Consequently, a detailed study of alluvial plain facies provides indications of local climatic conditions in the place of deposition, whereas fluvial systems only reflect climatic conditions of the upstream erosional catchments.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The mechanisms linking sensation and action during learning are poorly understood. Layer 2/3 neurons in the motor cortex might participate in sensorimotor integration and learning; they receive input ...from sensory cortex and excite deep layer neurons, which control movement. Here we imaged activity in the same set of layer 2/3 neurons in the motor cortex over weeks, while mice learned to detect objects with their whiskers and report detection with licking. Spatially intermingled neurons represented sensory (touch) and motor behaviours (whisker movements and licking). With learning, the population-level representation of task-related licking strengthened. In trained mice, population-level representations were redundant and stable, despite dynamism of single-neuron representations. The activity of a subpopulation of neurons was consistent with touch driving licking behaviour. Our results suggest that ensembles of motor cortex neurons couple sensory input to multiple, related motor programs during learning.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aims. The Antarctica Search for Transiting ExoPlanets (ASTEP) program was originally aimed at probing the quality of the Dome C, Antarctica for the discovery and characterization of exoplanets by ...photometry. In the first year of operation of the 40 cm ASTEP 400 telescope (austral winter 2010), we targeted the known transiting planet WASP-19b in order to try to detect its secondary transits in the visible. This is made possible by the excellent sub-millimagnitude precision of the binned data. Methods. The WASP-19 system was observed during 24 nights in May 2010. Once brought back from Antarctica, the data were processed using various methods, and the best results were with an implementation of the optimal image subtraction (OIS) algorithm. Results. The photometric variability level due to starspots is about 1.8% (peak-to-peak), in line with the SuperWASP data from 2007 (1.4%) and higher than in 2008 (0.07%). We find a rotation period of WASP-19 of 10.7 ± 0.5 days, in agreement with the SuperWASP determination of 10.5 ± 0.2 days. Theoretical models show that this can only be explained if tidal dissipation in the star is weak, i.e. the tidal dissipation factor Q'★ > 3×107. Separately, we find evidence of a secondary eclipse of depth 390 ± 190 ppm with a 2.0σ significance, a phase that is consistent with a circular orbit and a 3% false positive probability. Given the wavelength range of the observations (420 to 950 nm), the secondary transit depth translates into a day-side brightness temperature of 2690-220+150 K, in line with measurements in the z′ and K bands. The day-side emission observed in the visible could be due either to thermal emission of an extremely hot day side with very little redistribution of heat to the night side or to direct reflection of stellar light with a maximum geometrical albedo Ag = 0.27 ± 0.13. We also report a low-frequency oscillation in phase at the planet orbital period, but with a lower limit amplitude that could not be attributed to the planet phase alone and that was possibly contaminated with residual lightcurve trends. Conclusions. This first evidence of a secondary eclipse in the visible from the ground demonstrates the high potential of Dome C, Antarctica, for continuous photometric observations of stars with exoplanets. These continuous observations are required to understand star-planet interactions and the dynamical properties of exoplanetary atmospheres.
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FMFMET, NUK, UL, UM, UPUK
Zika virus (ZIKV) is a flavivirus that is responsible for the current epidemic in Brazil and the Americas. ZIKV has been causally associated with fetal microcephaly, intrauterine growth restriction, ...and other birth defects in both humans and mice. The rapid development of a safe and effective ZIKV vaccine is a global health priority, but very little is currently known about ZIKV immunology and mechanisms of immune protection. Here we show that a single immunization with a plasmid DNA vaccine or a purified inactivated virus vaccine provides complete protection in susceptible mice against challenge with a strain of ZIKV involved in the outbreak in northeast Brazil. This ZIKV strain has recently been shown to cross the placenta and to induce fetal microcephaly and other congenital malformations in mice. We produced DNA vaccines expressing ZIKV pre-membrane and envelope (prM-Env), as well as a series of deletion mutants. The prM-Env DNA vaccine, but not the deletion mutants, afforded complete protection against ZIKV, as measured by absence of detectable viraemia following challenge, and protective efficacy correlated with Env-specific antibody titers. Adoptive transfer of purified IgG from vaccinated mice conferred passive protection, and depletion of CD4 and CD8 T lymphocytes in vaccinated mice did not abrogate this protection. These data demonstrate that protection against ZIKV challenge can be achieved by single-shot subunit and inactivated virus vaccines in mice and that Env-specific antibody titers represent key immunologic correlates of protection. Our findings suggest that the development of a ZIKV vaccine for humans is likely to be achievable.
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IJS, KISLJ, NUK, UL, UM, UPUK
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