myMUSCLE, a New Multiphysics, Multiscale Simulation Coupling Environment

Increasing the computational power enables the nuclear community to combine existing knowledge on the variety of different physical phenomena that take place in reactors and to develop tools that can simulate these combined, interacting phenomena simultaneously. This includes phenomena related to structural mechanics, fluid dynamics, and reactor physics among others. Coupling different codes developed specifically for the analysis of separate phenomenon is currently a topic high on the research and development agenda of the international community.

Based on the experience of successfully computing the dissymmetric benchmark in the Phénix reactor by coupling the system thermal-hydraulic (STH) code SPECTRA to the computational fluid dynamics (CFD) code CFX in the H2020 SESAME project, the Nuclear Research and Consultancy Group (NRG) is currently developing the code-coupling tool myMUSCLE: MultiphYsics MUltiscale Simulation CoupLing Environment. MyMUSCLE is an independent, external, Fortran-based code that arranges the efficient and robust coupling of different codes. It aims at being flexible with respect to the codes being coupled, i.e., commercial and open-source codes, while having a single coupling tool that enhances quality assurance. It is currently set up to couple SPECTRA as a STH code to CFX, Fluent, STAR-CCM+, or OpenFOAM as a CFD code. This paper presents the proof of principle and first verification of the myMUSCLE tool under development by applying it to multiscale thermal-hydraulic applications.

First, a flow through a pipe is modeled as proof of principle for explicit coupling at a single coupling interface. Second, in preparation for modeling liquid-metal-cooled fast reactors, a piping system with a pool with natural convection is modeled. The results of the multiscale calculations show good agreement among the different coupled CFD codes. Finally, the preparations for simulating the TALL-3D experiment, used for generating data for validation of simulation tools for liquid-metal pools, are presented.