Authors: Misun Min (Argonne National Laboratory (ANL)); Yu-Hsiang Lan (University of Illinois); Paul Fischer (University of Illinois, Argonne National Laboratory (ANL)); Elia Merzari (Pennsylvania State University, Argonne National Laboratory (ANL)); Stefan Kerkemeier (Argonne National Laboratory (ANL)); Malachi Phillips and Thilina Rathnayake (University of Illinois); April Novak (Argonne National Laboratory (ANL)); Derek Gaston (Idaho National Laboratory); Noel Chalmers (AMD Research); and Tim Warburton (Virginia Tech)
Abstract: Nek5000/RS, a highly-performant open-source spectral element code, has recently achieved an unprecedented milestone in the simulation of nuclear reactors: the first full core computational fluid dynamics simulations of reactor cores, including pebble beds with 352,625 pebbles and 98M spectral elements (51 billion gridpoints), advanced in less than 0.25 seconds per Navier-Stokes timestep. The authors present performance and optimization considerations necessary to achieve this milestone when running on all of Summit. These optimizations led to a four-fold reduction in time-to-solution, making it possible to perform high-fidelity simulations of a single flow-through time in less than six hours for a full reactor core under prototypical conditions.
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