Scalability of a Large Eddy Simulation Immersed Boundary solver on LUMI-C

The present project is aimed at demonstrating the scalability of an in-house, high-fidelity Large-Eddy Simulation, Immersed-Boundary solver in MPI Fortran language on the LUMI-C cluster, in order to provide evidence of its portability and suitability for future production runs on this system. The results of strong and weak scaling tests will serve for preparing a future proposal to the coming cut-off date of the EuroHPC JU Regular Access (November 2022), with the purpose of studying innovative, bio-inspired propellers, in the framework of an EU-funded research project. These propellers feature tubercles at the leading edge of their blades, as those on the fins of whales. Their purpose is achieving improved performance, compared to conventional design, by disrupting the coherence of the vortices generated at the leading edge of the propeller blades. Finite-differences are utilized to discretize the filtered Navier-Stokes equations. An immersed-boundary methodology enables the use of regular grids, as Cartesian or cylindrical, making the decomposition of the overall flow problem into subdomains very straightforward, efficient and suitable to parallel computing. Communications across subdomains are handled via calls to MPI libraries. I/O operations are performed using calls to parallel HDF5 libraries. The solver is not I/O intensive, with I/O operations taking only about 5% of the overall computational cost of a typical simulation. Although the scalability of the present solver was already tested on several, different architectures, also part of the PRACE and EuroHPC JU infrastructures (Marconi KNL, Joliot-Curie KNL, Joliot-Curie SKL, Joliot-Curie Rome, MareNostrum 4, Vega CPU, Karolina), the test-case that will be considered in this project will be specifically designed to be representative of the computational effort of the problem we aim to tackle in the framework of our next proposal for EuroHPC JU Regular Access.