Accepted

Articles recently accepted for publication:

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Confined sheared flows of hard and soft granular materials: some challenges in tribology and fault

Guilhem Mollon , Adriana Quacquarelli , Yinyin Zhang , Nathalie Casas , Olivier Bouillanne , Alizée Madrignac, and Kévin Daigne

This paper belongs to a special issue dedicated to Challenges in Granular Matter. As such, it does not report any new finding, but rather offers an overview of the state of the art and on current and future challenges for the granular physics community. The focus is put on the case of confined sheared flows of granular samples with particular complexities, such as soft, angular, or cemented grains, with applications in tribology and fault mechanics. We first explain why the granular science may help to improve our understanding of dry friction in these two applications, and illustrate some recently unveiled aspects of the complexity of the problem. We then describe a few avenues for future research on the topic, focusing on the
dialog between simulations and experiments, on the scale-related challenges, and on some pivotal computational aspects.

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Future challenges on focused fluid migration in sedimentary basins: insight from field data, laboratory experiments and numerical simulations

A Gay and V Vidal

In a present context of sustainable energy and hazard mitigation, understanding fluid migration in sedimentary basins – large subsea provinces of fine saturated sands and clays – is a crucial challenge. Such migration leads to gas or liquid expulsion at the seafloor, which may be the signature of deep hydrocarbon reservoirs, or precursors for violent sub-sea fluid releases. If the former may orient future exploitation, the latter represent strong hazards for anthropic activities such as offshore production, CO2 storage, transoceanic telecom fibers or deep-sea mining. However, at present, the dynamics of fluid migration
in sedimentary layers, in particular the upper 500 m, still remains unknown in spite of its strong influence on the fluid distribution at the seafloor. Understanding the mechanisms controlling the fluid migration and release needs the combination of accurate field data, laboratory experiments and numerical simulations. Each technique shall lead to the understanding of the fluid structures, the mechanisms at stake, and a deep insight on the fundamental processes ranging from the grain scale to the kilometers-long natural pipes
in the sedimentary layers. Here we review the present available techniques, advances and challenges still open for the geosciences, physics, and computer science communities.

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Calibration of DEM Simulations for Dynamic Granular Systems

C.R.K. Windows-Yule & A. Neveu

Calibration and validation represent crucial but often-overlooked ingredients in the successful
application of discrete element method (DEM) simulations. Without rigorous calibration/validation
protocols, the results of DEM simulations can be imprecise or even unphysical, yet all too often the
methods used by practitioners are at best cursory, and at worst entirely absent. As the particle-
handling industries show an increasing interest in DEM, it is vital that his issue is resolved, lest a
potentially powerful tool be written off by industry as unreliable. In this work, we provide a concise
overview of contemporary methods used in the calibration and validation of DEM simulations of
powder flows, providing practical insights into their strengths and weaknesses, and ideas for manners
in which they may be improved and/or rendered more easily adoptable in the future.

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