---
license: cdla-permissive-2.0
task_categories:
  - other
tags:
  - cfd
  - fluid-dynamics
  - surface-mesh
  - vtk
  - pressure
  - wss
---

# Hemolab Bench

A dataset of parameterized 3-D CFD surface meshes (UNSTRUCTURED_GRID, triangulated)
with per-vertex **pressure** and **wall shear stress (WSS)** fields.

Each sample corresponds to a distinct geometry generated from a 17-parameter family
(curvature, twist, taper, Reynolds number, Taylor number).
The dataset contains **49,660 samples**, all sharing the same triangulation topology
(9,600 triangles, 25,600 vertices).


## Train / Validation / Test split

The dataset ships with pre-built splits so experiments are reproducible
without re-implementing the shuffle logic.

| Split | Fraction | Approx. samples |
|-------|----------|-----------------|
| `train` | 80 % | ~40 000 |
| `validation` | 10 % | ~5 000 |
| `test` | 10 % | ~5 000 |

Splits are assigned by a deterministic shuffle of all CSV ids:

```python
import torch

all_ids = sorted(full_csv_ids)          # all ids, sorted ascending
g = torch.Generator().manual_seed(42)
perm = torch.randperm(len(all_ids), generator=g).tolist()
shuffled = [all_ids[i] for i in perm]

n = len(shuffled)
train_ids      = shuffled[:int(n * 0.8)]
validation_ids = shuffled[int(n * 0.8):int(n * 0.9)]
test_ids       = shuffled[int(n * 0.9):]
```

## Test-set band labels

Two categorical columns (`alpha_split`, `reynold_split`) are populated **only
for `test`-split rows** (they are `null` in train and validation). They indicate
which distribution region each test sample belongs to, enabling per-regime
evaluation.

### `alpha_split`

Bands are symmetric around zero (checked on |alpha|):

| Label | |alpha| range |
|-------|--------------|
| `IR2` | [0.000, 0.013] |
| `IR1` | (0.013, 0.040) |
| `ID`  | [0.040, 0.120) |
| `OD1` | [0.120, 0.160) |
| `OD2` | [0.160, 0.200] |

### `reynold_split`

| Label | Reynolds range |
|-------|----------------|
| `OD`  | [100, 150) ∪ (450, 500] |
| `ID`  | [150, 250) ∪ [350, 450] |
| `IR`  | [250, 350) |

## Usage

```python
from datasets import load_dataset

# Full dataset
ds = load_dataset("ibm-research/hemolab-bench")
ds_train = ds["train"]
ds_val   = ds["validation"]
ds_test  = ds["test"]

print(f"{len(ds_train)} train  |  {len(ds_val)} val  |  {len(ds_test)} test")

# Single split
ds_train = load_dataset("ibm-research/hemolab-bench", split="train")

```

Access a sample:

```python
sample = ds_train[0]

import numpy as np

points   = np.array(sample["points"]).reshape(25600, 3)   # (N, 3) xyz
pressure = np.array(sample["pressure"])                    # (N,)
wss      = np.array(sample["wss"]).reshape(25600, 3)       # (N, 3) vector

print(sample["reynolds"], sample["alpha"])
```

Access band labels (test split only):

```python
sample = ds_test[0]
print(sample["alpha_split"], sample["reynold_split"])  # e.g. "ID", "IR"
```

The shared mesh topology (cell connectivity) is stored once in `topology.parquet`
at the dataset root:

```python
import pandas as pd

topology = pd.read_parquet(
    "hf://datasets/ibm-research/hemolab-bench/topology.parquet"
)
cells = topology["cells"].to_numpy().reshape(-1, 4)  # (9600, 4) quad indices
```

## Dataset schema

| Column | Type | Shape | Description |
|--------|------|-------|-------------|
| `id` | int32 | — | Sample identifier (0-based) |
| `points` | float32 | 76800 (= 25600×3, flattened) | Vertex coordinates |
| `pressure` | float32 | 25600 | Per-vertex pressure |
| `wss` | float32 | 76800 (= 25600×3, flattened) | Per-vertex wall shear stress vector |
| `alpha` | float64 | — | Geometry parameter |
| `gammaY0`..`gammaY3` | float64 | — | Y-curvature parameters |
| `gammaZ0`..`gammaZ3` | float64 | — | Z-curvature parameters |
| `beta0`..`beta3` | float64 | — | Taper parameters |
| `noise` | float64 | — | Geometry noise level |
| `iseed` | int64 | — | Random seed used for geometry generation |
| `reynolds` | float64 | — | Reynolds number |
| `taylor` | float64 | — | Taylor number |
| `alpha_split` | string | — | Alpha band label (test rows only; `null` elsewhere) |
| `reynold_split` | string | — | Reynolds band label (test rows only; `null` elsewhere) |

## Citation

> TBD — paper/preprint forthcoming.

## License

[CDLA Permissive 2.0](https://cdla.dev/permissive-2-0/)