Geothermal energy is one of the most viable sources of renewable heat. However, the potential risk of induced seismicity associated with geothermal operations may slow down the growth of the geothermal sector. Previous research has led to significant progress in understanding fluid-injection-induced seismicity in geothermal reservoirs. However, an in-depth assessment of thermal effects on the seismic risk was generally considered to be of secondary importance. This study aims to investigate the relative influence of temperature and key geological and operational parameters on the slip tendency of pre-existing faults. This is done through coupled thermo-hydro-mechanical simulations of the injection and production processes in synthetic geothermal reservoir models of the most utilized and potentially exploitable Dutch geothermal reservoir formations: Slochteren sandstone, Delft sandstone and Dinantian limestone.

In our study, changes in the slip tendency of a fault can largely be attributed to thermo-elastic effects, which confirms the findings of recent studies linking thermal stresses to induced seismicity. While the direct pore pressure effect on slip tendency tends to dominate over the early phase of the operations, once pore pressure equilibrium is established in a doublet system, it is the additional stress change associated with the growing cold-water front around the injection well that has the greatest influence. Therefore, the most significant increase in the slip tendency was observed when this low-temperature front reached the fault zone. The distance between an injection well and a pre-existing fault thus plays a pivotal role in determining the mechanical stability of a fault. A careful selection of a suitable target formation together with an appropriate planning of the operational parameters is also crucial to mitigate the risk of induced seismicity. Besides the well-known relevance of the in situ stress field and local fault geometry, rock-mechanical properties and operation conditions exert a major influence on induced stress changes and therefore on the fault (re)activation potential during geothermal operations.

The as-built geometry and material properties of parts manufactured using Additive Manufacturing (AM) can differ significantly from the as-designed model and base material properties. These differences can be more pronounced in thin strut-like features (e.g., in a lattice structure), making it essential to incorporate them when designing for AM and predicting their structural behaviour. Therefore, the aim of this study is to develop a numerical model with realistic characteristics based on a thin strut-based test artefact and to use it accurately for estimating its compressive strength. Experiments on test samples produced by selective laser sintering in PA 1101, are used to calculate geometrical deviations, Young's modulus, and yield strength, which are used to calibrate the numerical model. The experimental and numerical results show that the numerical model incorporating geometrical and material deviations can accurately predict the peak load and the force-displacement behaviour. The main contributions of this paper include the design of the test artefact, the average geometrical deviation of the struts, the measured material data, and the developed numerical model.

Sea-level science has seen many recent developments in observations and modelling of the different contributions and the total mean sea-level change. In this overview, we discuss (1) the evolution of the Intergovernmental Panel on Climate Change (IPCC) projections, (2) how the projections compare to observations and (3) the outlook for further improving projections. We start by discussing how the model projections of 21st century sea-level change have changed from the IPCC AR5 report (2013) to SROCC (2019) and AR6 (2021), highlighting similarities and differences in the methodologies and comparing the global mean and regional projections. This shows that there is good agreement in the median values, but also highlights some differences. In addition, we discuss how the different reports included high-end projections. We then show how the AR5 projections (from 2007 onwards) compare against the observations and find that they are highly consistent with each other. Finally, we discuss how to further improve sea-level projections using high-resolution ocean modelling and recent vertical land motion estimates.

Faulted and fractured systems form a critical component of fluid flow, especially within low-permeable reservoirs. Therefore, developing suitable methodologies for acquiring structural data and simulating flow through fractured media is vital to improve efficiency and reduce uncertainties in modelling the subsurface. Outcrop analogues provide excellent areas for the analysis and characterization of fractures within the reservoir rocks where subsurface data are limited. Variation in fracture arrangement, distribution and connectivity can be obtained from 2D fractured cliff sections and pavements. These sections can then be used for efficient discretization and homogenization techniques to obtain reliable predictions on permeability distributions in the geothermal reservoirs. Fracture network anisotropy in the Malm reservoir unit is assessed using detailed structural analysis and numerical homogenization of outcrop analogues from an open pit quarry within the Franconian Basin, Germany. Several events are recorded in the fracture networks from the Late Jurassic the Alpine Orogeny and are observed to be influenced by the Kulmbach Fault nearby with a reverse throw of 800 m. The fractured outcrops are digitized for fluid flow simulations and homogenization to determine the permeability tensors of the networks. The tensors show differences in fluid transport direction where fracture permeability is controlled by orientation compared to a constant value. As a result, it is observed that the orientation of the tensor is influenced by the Kulmbach Fault, and therefore faults within the reservoirs at depth should be considered as important controls on the fracture flow of the geothermal system.

The excavation of a tunnel through a mudstone formation provides an opportunity to examine the effects of the modification of the physical and chemical environment on the rock. The mineralogical and chemical consequences of hydration-dehydration cycles and of oxidation have been evaluated in the case of the Toarcian mudstone formation at the Tournemire experimental site (France). Studies by X-ray diffraction and tansmission electron microscopy of both altered and preserved samples show that the introduction of air and condensed water causes the oxidation of pyrite and the subsequent generation of acid and sulphate-rich waters at the micron scale, in the local environment of pyrites. The fluid-clay particle interactions around the oxidized pyrites induce: (1) a statistical enrichment in Si of the I-S clay minerals; (2) an increase in the Fe(III)/Fe total ratio in some of the I-S particles; and (3) the dissolution of illite layers in mixed-layer I-S. These evolutions are consistent with the results of numerical modelling which reproduced the interaction between the clay particles and the acid water.

The generation and migration of gas within and around proposed radioactive waste disposal facilities is potentially a safety critical process. A safety case for a facility that generates significant quantities of gas (e.g. through metal corrosion or radiolysis) will require demonstration that gas migration around and away from the waste is sufficiently understood and will not breach the safety case for the facility. Models can be used to understand the likely hydraulic evolution of such a disposal facility, but the models need to consider processes over a range of scales. A whole repository may extend over kilometres, with individual disposal cells at the scale of tens of metres and features which provide pathways for gas migration on a centimetre scale. All of these features may be significant from a safety perspective and capturing the impact of all of these features in a single model is a significant challenge.

This paper presents an approach to tackling this multi-scale problem, which allows the whole repository to be modelled in a computationally efficient manner. The approach involves identifying areas within the modelled domain that show very similar behaviour, and representing these areas with sub-models, so that small-scale features are retained, but computational overhead is decreased by using the results in more than one location in the model domain. The approach allowed a model of a whole repository to be run on a single processor core, whilst maintaining the small-scale features of the system. The model results were compared against more conventional upscaling techniques and show the advantage of a more detailed representation of small-scale features. The model results reflect the conceptual understanding of how gas would migrate in a repository.

The study of astrophysical maser formation provides a useful probe of the chemical composition and physical conditions of the sources they are observed in. This exploration requires continuously solving the SE equations for the populations of the energy levels in search of conditions that will produce an inversion. After evaluation of available implementations applying the Escape Probability approximation, the masers solver was developed to provide an efficient and robust matrix inversion calculation. This open source package is hosted at https://bitbucket.org/ruby_van_rooyen/masers.

The interaction of femtosecond ultra-intense laser pulses with clusters increases absorption of the incident laser light compared with the interaction with solid targets and leads to enhanced generation of different quantum beams with unique parameters. Future investigations of such interaction urgently need detailed modeling and optimization of cluster parameters, for instance, in order to obtain the clusters with desired size, or some specific spatial configuration of the target etc. A numerical model of gas-cluster targets production by the nozzle flows of gases and binary mixtures is presented. Some previous results of the model utilization are summarized, and some new results are given. Techniques of experimental verification of the numerical results are discussed.

We present climate data, direct surface mass balance (SMB) observations and model results for Mocho Glacier in the Chilean Lake District. Mean annual temperature on a nunatak of Mocho Glacier at an elevation of ~2000 m was +2.6°C in 2006–15 and mean annual precipitation in Puerto Fuy (13 km from the glacier, at an elevation of 600 m) was 4000 mm for the same period. High interannual variations in the SMB of Mocho Glacier were observed. A simple SMB model is able to reproduce the observed annual variations in SMB, but fails to predict the steep observed mass-balance gradient. The average of the measured annual glacier mass balances in the four hydrological years 2009/10–2012/13 was −0.90 m w.e. a−1 and the average modelled annual glacier mass balance 2006/07–2014/15 was −1.05 m w.e. a−1. The observed distributed ablation shows a clear altitudinal dependency, while accumulation is determined by patterns of snow drift as well. These patterns are only poorly represented in the model and have to be included in order to be able to reproduce a realistic SMB map of the glacier.

Any future changes in the volume of Antarctica’s ice sheets will depend on the dynamic response of outlet glaciers to shifts in environmental conditions. In the Transantarctic Mountains, this response is probably heavily dependent on the geometry of the system, but few studies have quantified the sensitivity of these glaciers to environmental forcings. Here we investigated the controls, along-flow sensitivity and time-dependent dynamics of Skelton Glacier. Three key outcomes were: i) present-day flow is governed primarily by surface slope, which responds to reduced valley width and large bed undulations, ii) Skelton Glacier is more susceptible to changes in atmospheric temperature than precipitation through its effect on basal sliding near the grounding line, and iii) under conditions representative of Pliocene and Quaternary climates large changes in ice thickness and velocity would have occurred in the lower reaches of the glacier. Based on these new quantitative predictions of the past and present dynamics of Skelton Glacier, we suggest that similar Transantarctic Mountain outlet glaciers could experience greater ice loss in their confined, lower reaches through increased basal sliding and ocean melt under warmer-than-present conditions. These effects are greatest where overdeepenings exist near the grounding line.

Geomorphology as a scientific discipline has underwent major developments since the mid 20th century. From its original descriptive nature aiming to understand landscape evolution, it developed towards a more process-based oriented discipline. To a large extent this evolution followed a quantitative approach whereby modelling becomes more and more important. A schism between applied or engineering geomorphology and system-based geomorphology aiming at understanding landscape change emerges in the 1950-1960's. Only at the end of the 20th century – early 21st century, integration of quantitative field-based approaches on longer term issues of landscape evolution with numerical modelling emerges. This is particularly true for the Holocene for which the importance of human impact on geomorphic processes and landforms became acknowledged. With respect to landscape evolution on much longer timescales, the development of tectonic geomorphology becomes apparent. In this paper, some evolution of ideas and trends within geomorphology with respect to understanding landscape dynamics are summarised and put into the career perspective of Jef Vandenberghe.

Numerical modeling of molecular masers is necessary in order to understand their nature and diagnostic capabilities. Model construction requires elaboration of a basic description which allows computation, that is a definition of the parameter space and basic physical relations. Usually, this requires additional thorough studies that can consist of the following stages/parts: relevant molecular spectroscopy and collisional rate coefficients; conditions in and around the masing region (that part of space where population inversion is realized); geometry and size of the masing region (including the question of whether maser spots are discrete clumps or line-of-sight correlations in a much bigger region) and propagation of maser radiation. Output of the maser computer modeling can have the following forms: exploration of parameter space (where do inversions appear in particular maser transitions and their combinations, which parameter values describe a ‘typical’ source, and so on); modeling of individual sources (line flux ratios, spectra, images and their variability); analysis of the pumping mechanism; predictions (new maser transitions, correlations in variability of different maser transitions, and the like). Described schemes (constituents and hierarchy) of the model input and output are based mainly on the experience of the authors and make no claim to be dogmatic.

Mathematical modeling provides a particularly important tool for studying thestreamrunoff formation processes, and its role is enhanced in the case of a sparse,obsolete monitoringnetwork characteristic of most regions of Siberia. When analyzingspatio-temporal regularities ofthe water and sediment runoff in river systems, serious problems are caused bylack of the basichydrological model capable of handling real-time data of hydrologicalmeasurements.
Calculations of unsteady flows in stream channels draw heavily onone-dimensional numericalmodels which are relatively easy to use and yield reliable results. Numericalinvestigations into thehydraulic regime of natural streams involve specific difficulties caused by thepresence of nonlinearfrictional forces in a turbulent flow, a variability in the channel geometry,the braiding of flows, thepresence of floodplain depressions, riffles, etc. For especially complexstretches of rivers, a onedimensionalapproximation no longer fits the reality sufficiently adequately, so that theplanar flowstructure must be taken into account. For this purpose Saint Vennant's planesystem of equationswas used as the basis in order to develop further the numerical model due tothis author whichis intended for calculating the flow field, flow rates, levels, and impurityconcentrations in naturalwater bodies of an arbitrary configuration or in a part of them. Fundamentallaws of fluid mechanicsare used as the basis for the model.
Spatial modeling of flows in complex regions necessitates reliable, consistentmethods providingacceptable accuracy. As far as hydrological problems are concerned, the controlvolumemethod that allows the use of curvilinear grids was found to be the mostpowerful tool for obtainingthe initial finite-difference relations.
This paper offers a number of examples illustrating the capabilities of theplanar model forstreams which is intended to resolve real problems arising at the design,construction and operation stages of engineering structures in river channelsand floodplains.

Les antennes paraboliques ultra légères des satellites de télécommunication, sont fabriquées en matériaux composites à partir de coques multicouches très minces obtenues par tissage. Pendant la première phase de vol du lanceur, lors de la traversée des premières couches atmosphériques, les excitations vibro-acoustiques dues au système de propulsion et aux forces aérodynamiques sont les plus critiques. La charge acoustique de type aléatoire induite sur la structure de l'antenne, devient alors très importante et peut provoquer des dommages aux structures et aux équipements. Pour réduire les charges acoustiques, les concepteurs utilisent des coques micro-perforées pour permettre à la structure de "respirer" et de réduire ainsi la charge acoustique. Le dimensionnement et l'optimisation de ces structures nécessitent des outils de calcul numérique. La prise en compte de la perforation du matériau pour le calcul de la charge induite par l'excitation acoustique aléatoire n'est pas classique. L'objet de cette étude est de proposer un modèle d'impédance locale représentatif de la micro-perforation pouvant être utilisé dans un code de calcul vibro-acoustique.

Le procédé de formage électromagnétique, electromagnetic forming process ou EMF en anglais, consiste à déformer les métaux en appliquant une pression générée par un champ magnétique variable d'une grande intensité. L'utilisation de ce procédé en complément de la mise en forme par emboutissage d'une ébauche, permet d'accroître la quantité d'aluminium employé dans la construction automobile en améliorant la formabilité des tôles et en réduisant les coûts de production. L'objectif des travaux de recherche liés à ce procédé est d'aboutir à une meilleure compréhension du mécanisme de déformation afin de développer des équipements et des méthodes efficaces pour sa mise en œuvre industrielle. Une manière de parvenir à cet objectif est l'utilisation de la simulation numérique au travers d'une modélisation du procédé basée sur la méthode des éléments-finis. Ces travaux de développement ont été partiellement menés dans le cadre d'un projet européen appelé EMF (G3RD-CT-2002-00798).

Although sophisticated geochemical studies tell us that tonolite-trondhjemite-granodiorite (TTG) plutonic complexes must be formed by partial melting of metabasaltic source material, they cannot tell us the tectonic regime in which this crust was formed, nor how large volumes of TTG magma can be generated. This study suggests that a solution to TTG arc crust formation requires a strongly interdisciplinary approach, to resolve the tectonic setting (slab melt verses mafic lowermost crust sources), the time and length scales for melting and extraction, and the role of melt segregation mechanisms in the formation of both Archean TTGs and more recent adakite-like magmas. The aim of this paper is to present an experimental approach which, when coupled with numerical models, allows some of these issues to be addressed. The experiments are designed to reproduce the local changes in bulk composition that are predicted to occur in response to buoyancy-driven melt segregation along grain edges and associated compaction of the solid residue. The preliminary study presented here documents the changes we observe in the melt composition and melt and solid phase modes between earlier direct partial melting and the new segregation equilibration experiments on metabasalt bulk compositions. The results suggest that if dynamic melt segregation and equilibrium processes are active, they may modify the normally robust geochemical indicators, such as Mg-numbers, which are typically used to develop models of TTG petrogenesis.

La solidification des alliages binaires est problématique dans la mesure où de nombreuses hétérogénéités susceptibles de fragiliser le produit apparaissent. Ces hétérogénéités peuvent être à la fois de composition (appelées ségrégations) et de structures. Les ségrégations présentent, en outre, l'inconvénient d'apparaître aussi bien à l'échelle mésoscopique (freckles) qu'à l'échelle du lingot (macroségrégation). Il apparaît que la gravité joue un rôle prédominant dans la formation et le devenir des hétérogénéités observées. S'affranchir de cette composante peut être un des enjeux des nouveaux procédés de solidification. Par ailleurs, les alliages de titane-aluminium présentent une solidification péritectique : au cours de la solidification péritectique deux phases solides sont présentes dans le lingot. Un modèle numérique de solidification basé sur le moyennage statistique a été établi qui prend en compte la spécificité de ces alliages. Les calculs menés en condition de microgravité et de convection forcée montrent que la convection au voisinage du front de solidification influence la localisation des hétérogénéités.

Although sophisticated geochemical studies tell us that tonolite–trondhjemite–granodiorite (TTG) plutonic complexes must be formed by partial melting of metabasaltic source material, they cannot tell us the tectonic regime in which this crust was formed, nor how large volumes of TTG magma can be generated. This study suggests that a solution to TTG arc crust formation requires a strongly interdisciplinary approach, to resolve the tectonic setting (slab melt verses mafic lowermost crust sources), the time and length scales for melting and extraction, and the role of melt segregation mechanisms in the formation of both Archean TTGs and more recent adakite-like magmas. The aim of this paper is to present an experimental approach which, when coupled with numerical models, allows some of these issues to be addressed. The experiments are designed to reproduce the local changes in bulk composition that are predicted to occur in response to buoyancy-driven melt segregation along grain edges and associated compaction of the solid residue. The preliminary study presented here documents the changes we observe in the melt composition and melt and solid phase modes between earlier direct partial melting and the new segregation equilibration experiments on metabasalt bulk compositions. The results suggest that if dynamic melt segregation and equilibrium processes are active, they may modify the normally robust geochemical indicators, such as Mg-numbers, which are typically used to develop models of TTG petrogenesis.

Two models were used to assess the effects of coastal characteristics on radar propagation in ducting conditions in the Persian Gulf. The NCAR/Penn State MM5 model simulated atmospheric conditions at a 5-km horizontal spatial and hourly temporal resolution on a day on which observations of ducts existed. The output from this model was input to the AREPS propagation model to produce radar coverage over coastal areas. Four factors influenced radar propagation: the sea breeze; coastal configuration; orography; and ambient wind. The sea breeze alone allowed propagation to extend about 100 km inland in a layer 200 m deep. When the breeze was aided by a following ambient wind the propagation layer extended for 150 km and was 400 m deep. A coastal indentation caused differences in depth and intensity of propagation over a distance of about 30 km parallel to the coast in which the indentation occurred. Steep near-coastal orography blocked radar propagation.