# CFDPre

```{raw} html
<div class="cfdpre-hero">
  <img src="_static/cfdprelogo.png" alt="CFDPre logo">
  <div class="cfdpre-hero-text">
    <p>Open-source boundary-layer mesh sizing for CFD — first layer height, growth
    ratio, and final layer thickness, computed with the correct correlations for
    internal (pipe/duct) and external (flat-plate/aero) flows.</p>
    <div class="cfdpre-badges">
      <a href="installation.html">Get started</a>
      <a href="https://pypi.org/project/cfdpre/">PyPI</a>
      <a href="https://github.com/phsheth/cfdpre">GitHub</a>
    </div>
  </div>
</div>
```

**CFDPre** is an open-source Python library for **boundary-layer mesh sizing** in
Computational Fluid Dynamics (CFD). Given your fluid, flow conditions, and target
$y^+$, it computes the three numbers you need to set up an inflation / prism layer
stack in a mesher such as **OpenFOAM** (`snappyHexMesh`), Fluent, or cfMesh:

- **First layer height** — the wall-adjacent cell thickness that achieves your target $y^+$
- **Growth ratio** — the geometric expansion ratio between successive layers
- **Final layer thickness** — the thickness of the outermost layer in the stack

Fluid properties are evaluated with [CoolProp](http://www.coolprop.org/), so you can work
with real fluids (air, water, fuels, refrigerants, …) at a given temperature and pressure
instead of hand-typing density and viscosity.

## Why it exists

Sizing the near-wall mesh is one of the most repeated calculations in wall-bounded CFD,
and getting it wrong quietly corrupts your turbulence model and wall functions. CFDPre
turns the full chain — fluid properties → Reynolds number → skin friction → wall shear →
friction velocity → first layer height → growth ratio — into a single call, with the
correct correlations for **internal (pipe/duct)** and **external (flat-plate/aero)** flows.

## Quick example

```python
from cfdpre import yhgrcalc

result = yhgrcalc(
    fluid="Air",
    temperature_c=50,
    pressure_bar=10,
    massflow_kgpersec=2.5,
    hydraulicdia_mm=125,
    target_yplus=1,
    num_layers=8,
)

print(result["first layer height [yh] [m]"])  # -> 5.21e-06
print(result["Growth Ratio"])                 # -> 3.66  (with a UserWarning: too aggressive)
```

## Installation

```bash
pip install cfdpre
```

## Where to next

```{raw} html
<div class="cfdpre-cards">
  <a class="cfdpre-card" href="installation.html">
    <strong>Installation</strong>
    <span>Requirements and install options</span>
  </a>
  <a class="cfdpre-card" href="quickstart.html">
    <strong>Quickstart</strong>
    <span>Internal and external flow, in code</span>
  </a>
  <a class="cfdpre-card" href="theory.html">
    <strong>Theory &amp; Methodology</strong>
    <span>Every formula CFDPre uses, derived and referenced</span>
  </a>
  <a class="cfdpre-card" href="api/reference.html">
    <strong>API Reference</strong>
    <span>Full yhgrcalc signature and outputs</span>
  </a>
</div>
```

## Coming soon

CFDPre currently gives you the numbers — what's next is wiring them straight into your
mesher's config:

- **OpenFOAM** — generate a ready-to-paste `addLayersControls` / `snappyHexMeshDict` snippet
- **Fluent / cfMesh** — equivalent inflation-layer setup snippets
- **Batch / parametric sweeps** — vary velocity or geometry over an array and get a table of results

## Links

- **Source code:** <https://github.com/phsheth/cfdpre>
- **PyPI:** <https://pypi.org/project/cfdpre/>
- **Users group:** <https://groups.google.com/g/cfdpre>

```{toctree}
:hidden:
:maxdepth: 2

installation
quickstart
theory
api/reference
```