Version 1.1 Update Notes

Version 1.1 improves numerical failure handling, vortex-example stability, macOS portability, and tutorial validation while preserving the existing input format and solver interfaces wherever possible.

Numerical and solver corrections

• The 3D vortex example recomputes its nonlinear right-hand side after startup extrapolation and uses a local final-step size without modifying the global time step.
• Periodic quadratic products use a 2/3 Fourier mask. An optional bounded tail-energy spectral vanishing-viscosity (SVV) filter can damp populated high modes; separate feedback states are maintained for the toroidal and poloidal potentials.
• The mapped far-field coefficient is removed after each vortex step, and all MPI ranks collectively abort if either potential becomes non-finite.
• Laplacian inversion null modes, transformed-input handling, FFT chopped-region checks, and dense-by-band storage bounds are corrected.
• Invalid chopping sizes, unsupported hyperviscosity powers, enabled hyperviscosity with a non-positive coefficient, malformed SVV controls, and invalid output intervals now fail during input parsing.

macOS and MPI portability

Homebrew GNU Fortran is supported without the Linux-only -mcmodel=medium flag. External libraries can be built from any working directory with explicit compiler choices:

FC=gfortran CC=cc BUILD_JOBS=2 ./external/CMake_build.sh
make

Documented and notebook MPI commands use portable mpirun -n; the validation tool adds OpenMPI-only flags at runtime when they are actually required. This also allows compatible MPICH installations to run the tutorials.

Validation gate

The standard gate validates six notebooks, twelve documentation pages, and 13 documented executable paths on the requested MPI rank count. It additionally runs matched low-viscosity SVV-off and SVV-on vortex cases and requires their final fields to differ. Representative zero-coefficient hyperviscosity, unsupported-power, and invalid-SVV inputs must also fail nonzero.

python3 tools/validate_tutorials.py --ranks 2

Notebook cells can also be executed when nbformat, nbclient, and a Python kernel are installed:

python3 tools/validate_tutorials.py --execute-notebooks --ranks 1

CI repeats the two-rank gate with GNU Fortran bounds checking, backtraces, and floating-point traps enabled.

Numerical limitations and tuning

• The current exact 2/3 de-aliasing applies to the periodic azimuthal and axial directions. The mapped radial quadratic product is not over-integrated; SVV can damp its high-mode tail but cannot undo radial energy already aliased into retained modes.
• The saved vortex sample field is vorticity magnitude, not a kinetic-energy spectrum. A velocity-spectrum diagnostic and resolution study are required before assessing a -5/3 inertial-range slope.
• With periodic 2/3 masking, svv_cutoff = 0.75 primarily targets the mapped radial tail. Use a cutoff below approximately 2/3 if the highest retained periodic bands should also participate, and retune the target and strength for the chosen Reynolds number and resolution.