Underworld3 v3.1.0

Highlights

• Units and Scaling System — first-class dimensional quantities across the solver stack: write models in physical units (Pa·s, km, K) and let the framework non-dimensionalise and re-dimensionalise automatically.
• Mesh Adaptation infrastructure — the Winslow mesh smoother and MMPDE mesh mover are now formally supported, providing the foundation for anisotropic adaptive remeshing workflows.
• 40+ merged feature PRs since v3.0.1 — including Nitsche BCs, mesh deformation capability gate, semi-Lagrangian improvements, projection enhancements, and Darcy sign-convention corrections.

Supported (validated)

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• Units and Scaling System — Pint-backed dimensional quantities, non-dimensionalisation, and unit-aware expression arithmetic.
• Winslow Mesh Smoother — Parallel-safe interior mesh smoothing (smooth_mesh_interior) — the foundation the adaptive movers and geometric multigrid build on.
• Constant Nullspace (singular scalar solvers) — SNES_Scalar.constant_nullspace returns the minimum-norm solution for pure-Neumann / closed-manifold scalar problems whose operator has a constant kernel (the singular Poisson case).

Preview (present, unguaranteed)

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• MMPDE Mesh Mover / Adaptive Remeshing — follow_metric / OT mesh movement and variable transfer for anisotropic mesh adaptation.
• Geometric Multigrid / FMG Preconditioner — Automatic geometric full-multigrid preconditioning for the SNES solvers on refinement meshes (the preconditioner property).

Bug Fixes

• Darcy transient velocity sign and sign-convention corrected (#255)
• Mesh variable arithmetic with unit-aware operands (#282, #283)
• Stokes bodyforce setter now accepts UWQuantity components (#284)
• Boundary normals and domain membership now track deformed meshes (#264)
• CLI -uw_* parameter overrides now apply regardless of platform (#280)
• PETSc IS size query during boundary rebuild avoided (#287)

New Features

• Mesh deformation capability gate — public mesh.deform() API with safe cache invalidation, replacing the internal mesh._deform_mesh() (#188)
• Nitsche boundary conditions for weakly-imposed constraints (#275)
• Semi-Lagrangian traceback with old-frame interpolation (#186)
• Monotone advection-diffusion options (#234)
• Projection linear solver enhancements (#281)

Improvements

• Mesh smoother and MMPDE mover robustness improvements (#190, #225, #228)
• Units system extended to cover mesh variable arithmetic and coordinate evaluation
• Stokes constrained solver parallel correctness (#265)

Breaking Changes

• mesh._deform_mesh() now raises if the mesh carries live variables — use the public mesh.deform() instead (#188)

Contributors

Thanks to everyone who contributed to this release: Louis Moresi, Thyagarajulu Gollapalli, Ben Knight, Neng Lu, Julian Giordani, Juan Carlos Graciosa, Saurabh Shukla, @tiannh7.