# Al Rihla CFD reproducible package

This package documents and reruns an exploratory OpenFOAM 13 CFD comparison of a stationary Al Rihla-shaped football with and without wall rotation. It is designed for Vicena Science Computer and Vicena Compute.

## What is included

- `notebook/Al_Rihla_CFD_reproducible.ipynb`: clean analysis and visualization notebook.
- `geometry/`: repaired, centered, approximately 0.22 m ball surface plus validation metadata.
- `mesh_tools/`: scripts used to repair/remesh the uploaded third-party surface.
- `compute/mesh/`: standalone mesh-only Vicena Compute bundle.
- `compute/nonrotating/`: standalone non-rotating URANS bundle.
- `compute/rotating/`: standalone 8 rev/s rotating URANS bundle.
- `results_compact/`: force histories, summary values, provenance, and compact final centre-plane fields.
- `docs/`: mesh investigation notes and methodology.

## Reproduce the included notebook

Open `notebook/Al_Rihla_CFD_reproducible.ipynb` in JupyterLab and run all cells. The notebook uses only compact included data and does not submit remote jobs.

## Submit a Vicena Compute job

From a Vicena Science Computer session:

```bash
cd compute/mesh
./submit.sh
```

Repeat from `compute/nonrotating` or `compute/rotating` for the flow cases. The included `remote_project_runner_template.py` files are unchanged Vicena Compute runner templates. Each folder contains its own `vicena_compute_bundle_spec.json` and complete source tree. The runner creates local state files after submission; those state files are intentionally not shipped.

Each `submit.sh` copies the single canonical remeshed STL from `geometry/` into its case immediately before submission. This avoids shipping four byte-for-byte copies of the same 12 MB mesh while keeping every compute bundle self-contained when it is submitted.

The flow bundles regenerate the validated layer-free mesh, run steady initialization, advance 0.05 s of URANS, record force coefficients, and export all saved `U` and `p` snapshots for wake movies.

## Validated reference configuration

- Ball diameter: 0.22 m
- Freestream: 25 m/s
- Reynolds number: 3.67e5 using nu = 1.5e-5 m2/s
- Rotating case: 8 rev/s about +z, spin parameter 0.221
- Mesh reference: 263,891 cells
- Turbulence model: k-omega SST URANS
- Maximum Courant number: 0.35

## Relation to the public case story

This archive is the latest compact, rerunnable companion for the 263,891-cell, 0.05 s reference cases. The public CFD application page also retains figures from earlier geometry, meshing, orientation, and transient pilot stages because they document how the workflow evolved. Use `results_compact/provenance.json` and `results_compact/summary.csv` as the authoritative identifiers and summary values for the cases packaged here.

## Important limitations

- The geometry is a repaired third-party visualization model, not a metrology-grade scan of an official match ball.
- Seam and macroscopic surface features are retained only to the accuracy present in the uploaded model.
- The mesh has no prism boundary layers.
- Robust first-order velocity convection and orthogonal pressure treatment were required for OpenFOAM 13 stability.
- The 0.05 s transient interval is short and is not sufficient for a production-quality spectral or statistical wake analysis.
- No mesh-independence, time-step-independence, or wind-tunnel validation has been completed.
- The calculated coefficients are comparative exploratory results, not certified aerodynamic data.

## Sharing and licensing

The derived football mesh is based on “Al Rihla Qatar 2022 World Cup football ball STL” by generalista3D (@adelin), published on Sketchfab under the Creative Commons Attribution 4.0 International license. The source was repaired, centered, scaled, remeshed, renamed, and prepared for exploratory CFD. Full attribution, source links, modification notes, and trademark notices are in `THIRD_PARTY_NOTICES.md`.

The remaining Vicena-authored package materials are supplied publicly for inspection and scientific reproducibility. No separate open-source license is granted for those materials by this package.
