---
license: other
license_name: mixed-cc-by-4.0-and-cc-by-nc-sa-4.0
license_link: LICENSE
task_categories:
  - other
language:
  - en
tags:
  - turbulence
  - rans
  - cfd
  - openfoam
  - dns
  - les
  - benchmark
pretty_name: "Closure Challenge v2 — CFD case files (heavy)"
size_categories:
  - 10B<n<100B
configs:
  - config_name: cc_by_4_0_cases
    data_files:
      - path:
          - data/alpha_*/**
          - data/AR_*/**
          - data/NASA_*/**
          - data/train/**
          - data/validation/**
        split: train
  - config_name: cc_by_nc_sa_4_0_cases
    data_files:
      - path:
          - data/ERCOFTAC_AhmedBody25/**
          - data/ERCOFTAC_WingBodyJunction/**
        split: train
viewer: false
---

# Closure Challenge v2 — CFD case files (heavy)

Companion dataset to [`anon-closure-challenge-v2/closure-challenge-v2`](https://huggingface.co/datasets/anon-closure-challenge-v2/closure-challenge-v2).

This repository hosts the **full OpenFOAM cases** (mesh, fields, run scripts), VTK volume snapshots, and DNS-native partitioned VTUs for the 14 test cases of the Closure Challenge v2 benchmark, together with the **standardized training and validation sets** under `data/train/` and `data/validation/`.

The lightweight integral-profile portion needed for reproducing the scoring protocol is in the [companion dataset](https://huggingface.co/datasets/anon-closure-challenge-v2/closure-challenge-v2). **Most reviewers and submitters do not need this heavy dataset** — it is only required for re-running the CFD simulations from scratch or for extended analyses.

NeurIPS 2026 Evaluations & Datasets track submission. Authors anonymised for double-blind review.

**Code repository** (scoring package, evaluation protocol, per-case attribution): <https://anonymous.4open.science/r/closure-challenge-v2>

## Contents

Approximately 17 GB. 14 test cases, plus 27 training and 5 validation cases. Every case carries a converged solution and the mesh it was computed on.

```
data/
├── alpha_05_4071_2024/         v1 PHLL   0/, 20000/, constant/, system/, postProcessing/
├── alpha_05_4071_4048/
├── alpha_15_13929_2024/
├── alpha_15_13929_4048/
├── AR_1_Ret_360/               v1 DUCT   0/, 405/, constant/, system/, caseDef, fieldDef
├── AR_3_Ret_360/                         0/, 1540/, ...
├── AR_14_Ret_180/                        0/, 7009/, ...
├── NASA_2DWMH/                 v1 hump   0/, 2000/, VTK/, constant/, system/
├── NASA_2DZP/                  v2 new    10000/, baseline_komegasst/, highfidelity/
├── NASA_2DN00/                           {10,15,17,18}deg/, baseline_komegasst/, highfidelity/
├── NASA_ASJ/                             0/, 0.25/, baseline_komegasst/, highfidelity/
├── NASA_FaithHill/                       0/, 0.orig/, 2000/, VTK/, plots/, ...
├── ERCOFTAC_AhmedBody25/                 0/, 30/, VTK/, plots/, ...
├── ERCOFTAC_WingBodyJunction/            0/, 5000/, VTK/, plots/, ...
├── high_fidelity_data/         raw upstream reference archives, per case
│
├── train/                      27 TRAINING cases
│   ├── alpha_*/                  21 parametric periodic hills
│   ├── AR_1_Ret_180/  AR_3_Ret_180/  AR_5_Ret_180/  AR_10_Ret_180/
│   ├── CBFS/                     curved backward-facing step
│   └── PH_Breuer/                periodic hill, Re=10595
│
└── validation/                 5 VALIDATION cases
    ├── alpha_05_10071_2024/  alpha_05_10071_4048/
    ├── alpha_15_7929_2024/   alpha_15_7929_4048/
    └── AR_7_Ret_180/
```

The 14 cases at the top level are the **held-out test set**. Training and
validation cases live under `train/` and `validation/` and carry the same
OpenFOAM structure.

Extraction and plotting utilities live at the top of `data/`:

```
extract_baseline_from_vtk.py    Probe baseline at high-fidelity reference points
extract_wbj_surface_lines.py    Wing-body junction surface line extraction
faith_hill_to_csv.py            FAITH hill PIV/PSP/FISF re-formatter
commented_dat_to_csv.py         Ahmed-format .dat to flat CSV
dat_to_csv.py                   NASA Tecplot zone-format .dat to flat CSV
```

Per-case `compute_forces.py`, `extract_surface_Cp.py`, and `run_hpc_slurm.sh` sit inside the relevant case directories.

## Standardized training track

The benchmark fixes a train / validation / test split so that methodologies can
be compared independently of the training data. All three parts are published
here.

```
data/<case>/          14 held-out TEST cases
data/train/           27 training cases
data/validation/       5 validation cases
```

| Split | Contents |
|---|---|
| test | 4 periodic hills, 3 ducts, NASA wall-mounted hump, 6 v2 engineering cases |
| training | 21 parametric periodic hills, 4 ducts (AR 1/3/5/10 at Re_tau=180), CBFS, PH_Breuer |
| validation | 4 parametric periodic hills, 1 duct (AR 7 at Re_tau=180) |

Training and validation cases carry the same OpenFOAM structure as the test
cases: `constant/polyMesh`, `system/`, initial and converged time directories,
and the high-fidelity reference fields (`U_LES`, `k_LES`, `tauij_LES`).

**Using any test case during training or validation is not permitted.** The
split above is the definition of the standardized track.

## Case notes

### Reading the periodic-hill case names

The digits in `alpha_<slope>_<Lx>_<Ly>` are **domain dimensions, not Reynolds numbers**. `alpha_05_4071_2024` has streamwise extent x = 0 .. 4.071 and wall-normal extent y = 0 .. 2.024; `alpha_15_13929_4048` spans x = 0 .. 13.929 and y = 0 .. 4.048. The leading `alpha` value is the hill-slope parameter.

### NASA_2DWMH

`NASA_2DWMH` is the NASA wall-mounted hump (2D), domain x = -0.851 .. 0.672, y = -0.420 .. 0.000, converged at t = 2000. Baseline is simpleFoam + kOmegaSST.

### Turbulence model

All 14 baselines are `simpleFoam` (or `rhoSimpleFoam` / `rhoPimpleFoam` for the compressible cases) with `RAS kOmegaSST`, no ML correction.

## License

This dataset aggregates material under two different licenses. See the `LICENSE` file at the repository root for the authoritative statement.

- **CC-BY-4.0**: the 12 non-ERCOFTAC test cases (`alpha_*`, `AR_*`, `NASA_*`) and everything under `data/train/` and `data/validation/`, derived from public-domain or CC-BY upstream sources (NASA Turbulence Modeling Resource, Vinuesa duct database, Xiao parametric periodic-hill database).
- **CC-BY-NC-SA-4.0**: `ERCOFTAC_AhmedBody25` and `ERCOFTAC_WingBodyJunction`, curated extracts of ERCOFTAC kbwiki material (Classic Collection case082; DNS 1-6), inheriting the upstream non-commercial and share-alike conditions.
- **Code**: extraction, plotting, and run scripts (`*.py`, `*.sh`) are MIT. See `LICENSE-CODE` in the [code repository](https://anonymous.4open.science/r/closure-challenge-v2).

Hugging Face has no per-directory license field, so this repository declares `license: other` and records the split in `LICENSE`. The `configs` block above groups the two license scopes for readers and machine consumers; it does not itself carry licensing force.

Per-case source attribution is in [`SOURCES.md`](https://anonymous.4open.science/r/closure-challenge-v2/SOURCES.md) of the code repository.

## Citation

```bibtex
@inproceedings{closure_challenge_v2_neurips26,
  title={The Closure Challenge: A Benchmark Task for Machine Learning in Turbulence Modeling},
  author={Anonymous},
  booktitle={NeurIPS Datasets and Benchmarks Track (under review)},
  year={2026}
}
```

## Croissant metadata

A Croissant 1.0 metadata file is provided as `croissant.json` in this repository.