Light Exascale Application (LEA): an exascale code for the simulation of compressible turbulent flows

This work presents the development of the Light Exascale Application (LEA), a compressible flow solver built to conduct direct-numerical simulation (DNS) and large-eddy simulation (LES) of turbulent flows. LEA is written in the C++ programming language, and uses the Kokkos framework for intra-node parallelism with MPI for inter-node parallelism. These features allow for LEA to achieve performance portability across modern heterogeneous platforms. Software design principles were used from the inception of LEA, enabling high levels of code flexibility and modularity. Results from benchmarking tests across several modern CPU- and GPU-based high-performance computing clusters are presented, considering weak and strong scaling. Tests are conducted with no platform-specific modifications or optimizations to the code base. Verification and validation studies for LEA are presented for a Taylor-Green vortex, a zero-pressure gradient flat plate turbulent boundary layer, and a compressible turbulent channel flow case. Numerical studies were completed with 2nd-to-4th order spatial operators, and 4th order time discretization. Performance profiling of LEA was conducted using the Kokkos-tools profiling suite, identifying various enhancements to the code base.