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Spatially resolved infectious disease models for localized outbreak mitigation (and efficient mathematical software)
No full textNumerical investigation of gas turbine combustor cooling performance with Bézier effusion holes
No full textA novel gas turbine combustor effusion hole concept was simulated under realistic fuel-lean operating conditions in the present work. The hole's bore was defined using a quadratic Bézier curve, enabling efficient cooling air injection over the liner. Modifications to the hole's inlet and width expansion were made to observe their effect on cooling performance. Results show that the addition of an inlet fillet increased velocity in the hole and improved flow attachment, but had marginal impact on liner temperature. A higher width expansion yielded greater cooling effectiveness and a more uniform surface heat flux distribution. A narrower injection hole generally increased streamwise jet momentum and resulted in lift-off and localized hot spots due to counter-rotating vortices. Complex effusion holes, such as those presented here, will be facilitated by advances in additive manufacturing and serve to improve the thermal efficiency of gas turbines
CAD-integration for Gradient-based Shape Optimization using the Algorithmically Differentiated pythonOCC Library
No full textpythonOCC is a library that provides Python bindings for the Open CASCADE Technology (OCCT) C++ geometric modelling kernel. To integrate it into a gradient-based shape optimization, one requires to compute the so-called geometric sensitivities, e.g., derivatives of surface nodes with respect to the design parameters. To obtain this information, pythonOCC and OCCT were algorithmically differentiated. Here, they are modularly integrated in the form of a CAD plugin into a framework for multidisciplinary design analysis and optimization (MDAO) based on the DLR's FlowSimulator HPC ecosystem. The CAD plugin allows a robust and metadata-enabled mesh-to-CAD association between MPI domain-decomposed mesh objects and the underlying CAD patches, as well as the computation of geometric sensitivities. The framework integration of pythonOCC is demonstrated in a context of gradient-based, aerodynamic shape optimization for a RAE2822 configuration in fully turbulent, transonic flow
Ultramafic float rocks at Jezero crater (Mars): excavation of lower crustal rocks or mantle peridotites by impact cratering?
No full textBased on observation and data from meteorites and in situ scientific missions, experiments as well as models, the Martian mantle is assumed to share some compositional and mineralogical affinity with the terrestrial mantle. However, there might be subtle differences like the Martian mantle being more ferroan. Yet, we do not have any direct analysis of a Martian mantle rock to confirm this assumption. NASA’s Perseverance rover found olivine-rich boulder-sized float rocks on the upper Jezero fan (Mars). These boulders have an ultramafic composition and their mineralogy is dominantly composed of Fo73±3 olivine with high-Mg orthopyroxene, Cr-rich Ti-Fe oxides and minor plagioclase and high-Ca pyroxene. Microtextural and petrological analysis reveals that these minerals crystallized at equilibrium. In addition, these boulders are different from all the bedrocks analyzed by Perseverance along its traverse which are crustal igneous rocks and sediments. Comparing our data to Martian meteorites and available Mars bulk silicate models (BSM), we discuss that these boulders could represent primitive melts and/or lower crustal material, and we specifically hypothesize that they could be mantle peridotites. We propose that these putative mantle rocks could have been excavated by the succession of impacts from the shallow mantle or lower crust in the Isidis region where Jezero crater is located. These olivine-rich boulders could thereby constitute the first direct analysis of a Martian mantle rock
A spatial and spectral Analysis of the Sentinel-2 nighttime Image
Full text linkNighttime optical remote sensing provides valuable insights into natural and, in particular, human activities. This study evaluates
the nighttime imaging capabilities of the Sentinel-2 mission using the only available nighttime acquisition not limited to ocean
observations for dark signal calibration, covering the United Arab Emirates with Dubai in 2015. We checked the detection limit
using granules over the Persian Gulf, extracted radiance spectra for different regions of interest, and analysed lighting types and
temperatures. Results suggest a conservative nighttime detection limit of approx. 0.37 W/m²/µm/sr for visible/near infrared bands,
and 0.08 W/m²/µm/sr for short-wave infrared bands. Sentinel-2’s high spatial resolution and multispectral bands, although designed
for daytime observations, were capable of detecting and classifying bright visible/near and short-wave infrared emitters. Comparisons with hyperspectral EnMAP imagery acquired in 2025 validated the classifications and revealed changes in urban lighting over
a decade. While limitations apply, this study highlights S2’s potential for nighttime remote sensing and supports considerations of
nighttime capabilities for future satellite missions
Valorization of phosphogypsum by-product as thermochemical energy storage material
No full textPhosphogypsum (PG), a phosphate industry by-product, emerges as a promising candidate among numerous materials capable of reversibly storing thermal energy via endo-exothermic reactions. By utilizing this resource, not only its environmental impact will be reduced, but the overall cost-effectiveness of the thermochemical energy storage (TcES) system will be improved. PG as characterized in this study is composed mainly of calcium sulfate (CS) dihydrate, CaSO4·2H2O. Its dehydration proceeds in two steps: first, transforming it into CS hemihydrate, CaSO4∙0.5H2O, with an enthalpy of 441 J/g, followed by dehydration to CS anhydrate, CaSO4, with an enthalpy of 147 J/g. Rehydrating the material allows complete energy recovery. The reversibility of PG's hydration and dehydration reactions for the working pair CaSO4/H2O is demonstrated in this study. The cycling stability of PG and pure CS as thermochemical energy storage materials is investigated on a mg-scale as well as in a TcES lab-scale reactor of 20 g storage material bulk. PG shows better cyclability characteristics compared to CS. Over 60 cycles of hydration/dehydration at 140 °C, PG exhibited good cycling stability, whereas a decrease in conversion was observed in CS. However, increasing the dehydration temperature resulted in reduced cyclability for both materials. This reduced cyclability is attributed primarily to the formation of an inactive anhydrous CS phase, anhydrite II. This phase formation occurs at lower temperatures in the case of CS when compared to PG, which explains the distinct behaviors of these materials during cycling. Additionally, CS tends to agglomerate more easily, while PG presents reduced agglomeration. This difference is attributed to the presence of SiO2 in PG, which was confirmed through a three-cycle hydration/dehydration experiment comparing CS and CS with the addition of 10 wt% SiO2. PG also allows for a significant thermal heat upgrade, which was demonstrated in the lab-scale reactor during 26 cycles of hydration and dehydration, holding significant potential for various industrial applications, including waste heat recovery
An unstructured high-order finite-volume scheme for the simulation of reactive multi-species flows
Full text linkIn this work, a high-order finite-volume method is combined with an iterative projection approach to solve transport equations for reactive fluids in the low-Mach number regime. The proposed solution algorithm is fully collocated in both space and time and employs a vertex-centered -exact discretization to achieve truly third-order spatial accuracy, even on fully unstructured median-dual grids. To enhance both accuracy and robustness, viscous and convective fluxes are treated consistently within the high-order framework. Convective fluxes are discretized using a central face-value approximation augmented with adaptive numerical dissipation control, governed by a novel gradient-limiting strategy that selectively reduces the order of accuracy near strong gradients while minimizing artificial dissipation elsewhere. The performance of the method is assessed against a conventional finite-volume scheme for unstructured grids, with a focus on reducing the number of computational elements required for accurate simulations. Benchmark test cases include the isochoric advection of a hydrogen-oxygen mixture, convection of a pseudo-isentropic vortex, and flame kernel–vortex interaction. As a key extension, a large-eddy simulation of a turbulent hydrogen-nitrogen-air diffusion flame on a fully unstructured three-dimensional grid is presented, demonstrating the method’s capability to handle complex variable-density reactive flows in practical combustion scenarios. Results show that the k-exact scheme achieves accurate predictions even on relatively coarse grids, substantially reducing computational cost while maintaining physical fidelity - underscoring its potential for reactive flow simulations in both industrial and research applications
From Analog Tests to the Moon: Situational Awareness Systems for Astronauts and Tourists
No full textHuman space exploration is entering a new phase with the Artemis program and the planned return to the Moon. Efficient and scientifically valuable Extra-Vehicular Activities (EVAs) in the lunar environment require advanced Mission Support Systems (MSS) that enhance astronaut autonomy, safety, and situational awareness. This study presents the development and evaluation of a custom MSS tailored for lunar surface operations. The system was implemented and tested during a high-fidelity simulated EVA at the LUNA analog facility operated by DLR and ESA. Core functionalities included realtime crew tracking, workload monitoring, a QR-code-based inventory management system (IMS), and structured scientific documentation. All components were integrated into a webbased dashboard accessible by the astronauts and the Flight Control Team (FCT). The qualitative evaluation, based on video and voice recordings from the simulation as well as post-mission feedback by all participants, revealed specific strengths and limitations of the system, informing targeted design improvements to enhance usability, robustness, and procedural integration. The findings indicate that real-time tracking supported improved orientation and navigation across the simulated terrain. Physiological monitoring enabled real-time assessment of crew workload, which was considered beneficial for maintaining procedural awareness and supporting safety-critical decisions. QRcode- based inventory interaction enabled reliable identification and contextual linking of tools and samples. This contributed to procedural efficiency by reducing otherwise required feedback loops and manual logging, while also improving accuracy in tool usage and sample tracking throughout the EVA. The integrated documentation tools were seen as reducing cognitive load and streamlining post-EVA reporting processes. In addition to professional use cases, the potential application of such systems in the context of lunar tourism was examined. Based on operational observations and system interactions during the simulation, several design improvements were proposed to optimize human-system interaction and technical reliability while better aligning with operational workflows. These include higher levels of automation to facilitate safe and autonomous work with mission procedures. The results also highlight the potential of modular MSS architectures to evolve from specialized tools for scientific exploration into flexible platforms capable of supporting diverse user groups, including commercial spaceflight participants. This adaptability contributes to a broader vision of inclusive and sustainable lunar surface operations
A Discontinuous Galerkin Discretization for the Intrinsic Beam Model
No full textWith the Versatile Aeromechanic Simulation Tool (VAST), the German Aerospace Center (DLR) is developing a software framework for the simulation of rotary-wing aircraft. One challenge consists of simulating the dynamic behaviour of rotor blades. In general, rotor blades can be considered as flexible beams for which numerous models have been developed in the past. One of them is the geometrically exact intrinsic beam model derived by Hodges (AIAA J. 41(6):1131, 2003). It is represented by a time dependent hyperbolic system of partial differential equations (PDE) in one space dimension. In contrast to other well-known models like the EulerBernoulli model or the Timoschenko model, the governing equations of the intrinsic beam model contain non-linearities which makes it a geometrically exact model. This allows to model also beams undergoing large deflections making it well-suited for the simulation of rotor blades. We derive an energy stable discontinuous Galerkin (DG) approach for its discretization based on the approach in Kopriva and Gassner (SIAM J. Sci. Comput. 36(4):A2076, 2014)
