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Models have historically represented fractured porous media with continuum descriptions that characterize the media using bulk parameters. The impact of small-scale features is not captured in these models, although they may be controlling the performance of subsurface applications. Pore-scale models can simulate processes in small-scale features by representing the pore space geometry explicitly but are computationally expensive for large domains. The alternative multiscale approach entails the combination of pore-scale and continuum-scale descriptions in a single framework. We use Chombo-Crunch, a computational capability that discretizes complex geometries with an adaptive, embedded boundary method to contrast these two approaches. Chombo-Crunch takes advantagemore » of recent computational performance and memory bandwidth improvements resulting from the emergence of exascale computing resources. These combined improvements enable the efficient simulation of reactive transport in fractured media with a high degree of fidelity and the ability to capture the control small-scale processes exert on the overall medium evolution.« less

The recent arrival of the Frontier Supercomputer at Oak Ridge National Laboratory officially marked the dawn of the exascale computing era. Its successful deployment coincided with the culmination of the U.S. Department of Energy Exascale Computing Project (ECP), an ambitious, complex, and risky research and development effort that integrated contributions from a broad and diverse subset of the high-performance computing community. The success of ECP will ultimately be judged by the scientific and engineering advances that it enabled. In conclusion, this Special Issue is focused on showcasing early successes in the use of exascale resources to enable breakthroughs in keymore » areas of science in engineering.« less

Surface abrasion has been shown to create altered surface layers (ASLs) that are hundreds of nm thick on all types of Al alloys. Such ASLs have lower corrosion resistance than the underlying substrate of Al-Zn-Mg-Cu alloys. Here, we demonstrate how heat treatments affect the ASL microstructure on abraded Al-Zn-Mg-Cu alloys using transmission electron microscopy and atom probe tomography, and also how the corrosion properties change using electrochemical polarization. Additionally, high temperature treatments on the abraded bulk samples enhance η phase precipitation in the ASL, leading to a decreased Zn content in the ASL solid solution, which ennobles the ASL breakdownmore » potential.« less