](LICENSE) 
GPU-accelerated incompressible Navier–Stokes solver for flow in complex geometry, built around a staggered MAC grid, a signed-distance-field (SDF) description of the solid, a cut-cell Immersed Boundary Method, and a pressure-projection step with a geometric multigrid Poisson solve. The code is written in Kokkos C++ (one source runs on the CUDA, HIP/AMD, and OpenMP backends, selected at build time) and exposed to Python through nanobind (zero-copy, on core's View↔ndarray bridge); simulations are driven from Python.
The repository is also known as
pnm_from_sdf(its GitLab origin) — it computes pore-network–scale flow directly from segmented SDF geometry.
Modules
| Module | Role |
|---|---|
**flow** | The CFD solver — a distributed (MPI-optional) GPU cut-cell IBM Navier–Stokes solver in physical units, built on the shared core block-decomposition + async halo layer. One code / one API / MPI-optional, with native domain boundary conditions. Exposes peclet.flow.Solver (staggered MAC, default) and peclet.flow.SolverColocated (collocated/cell-centered velocities, ABC approximate projection) — identical API via a GridLayout policy. Validated against analytics and Zick & Homsy sphere-array drag (scripts/validate_zick_homsy_sdflow.py). |
**pnm** | Pore-network extraction — SDF VTI reading + pore/segmentation/topology extraction (SDFReader, extract_pores, segment_volume, extract_topology_gpu). The repo's namesake "pnm_from_sdf" feature. |
The original CUDA implementation has been retired (Kokkos became canonical, 2026-06); flow was validated bit-identical to the CUDA solver — to machine precision, and against Zick & Homsy sphere-array drag — before the CUDA sources were deleted (restore point: git tag pre-cuda-retirement). The shared cut-cell IBM primitives now live in src/cut_cell_ibm.hpp; the operator headers are src/mac_*.hpp + src/flow_ibm.hpp.
Capabilities
- Geometry: SDF solids (negative inside); the cut-cell IBM applies a Robust-Scaled no-slip / moving-wall condition and a matching cut-cell pressure operator (face openness from the SDF).
- Native domain boundary conditions (
flow): per-face periodic / no-slip wall / Dirichlet velocity (inflow) / outflow, plus per-position inlet velocity profiles. Validated on the lid-driven cavity (Ghia et al.), the developing plane channel (Poiseuille), and the backward-facing step (Armaly/Gartling). - Pressure multigrid: rediscretized geometric V-cycle, grid-independent, with MG-PCG and Chebyshev outer accelerators. Works on periodic, IBM, and non-periodic (BC) domains, including semi-coarsening for thin (quasi-2D) grids.
- Time integration: pressure projection with optional incremental pressure, explicit (Koren) or implicit-deferred-correction advection, and Picard outer iteration.
Build
<backend> is one of nvidia-cuda / host-openmp / lumi-hip under ../extern/install/, produced once by ../tools/bootstrap_deps.sh (a hard build dependency). Requirements: a Kokkos backend (CUDA/HIP/OpenMP — CUDA is just one option, not required), a C++20 host compiler, nanobind + scikit-build-core, and — for distributed flow — MPI. Python dependencies live in a virtual environment (.venv).
Run / verify
Simulations are scripts, not C++ mains. The scripts/verify_*_sdflow.py files are the canonical verification entry points:
Documentation
API documentation (C++ classes/kernels and Python scripts) is generated with Doxygen and published to GitHub Pages by the Documentation CI workflow. Build it locally with:
The architecture, conventions, and design rationale are described in CLAUDE.md and the design notes under doc/ in the repository.
