Scaling WaterLily.jl with MPI and an improved geometric multigrid solver

We present recent performance-oriented developments in this http URL, a scale-resolving incompressible flow solver written in pure Julia that runs seamlessly on CPUs and GPUs of any vendor.

Supported by the newly added MPI-based parallelism, strong-scalability tests display a near-ideal linear trend, and weak-scaling efficiency is kept above 85\% before node memory-concurrency contention dominates parallel performance.

Inter-node weak scalability is sustained above 96\% with grid size up to 1 billion cells.

We further benchmark improvements to the geometric multigrid Poisson solver enabled by an adaptive under-relaxed red-black Gauss--Seidel smoother together with anisotropic coarsening operators.