simbl

Compressible similarity boundary layer solver with Falkner-Skan and Falkner-Skan-Cooke support.

Install

pip install similarity-bl

Quick Start

API:

from simbl import SimilarityInputs, SolverOptions, solve_similarity

inputs = SimilarityInputs(mach_edge=6.0, temp_edge=55.0, wall_bc="adiabatic")
options = SolverOptions()

solution, info = solve_similarity(inputs, options)
print(f"f''(0) = {solution.fpp[0]:.6f}")
print(f"g(0)   = {solution.g[0]:.6f}")

CLI:

simbl init                   # generate a template config file
simbl solve config.toml      # solve from config
simbl solve --mach 6.0 --temp-edge 55.0 --wall adiabatic

Documentation

Full documentation: https://uahypersonics.github.io/similarity-bl

Citation

If you use simbl in your research, please cite it:

@software{simbl,
  author = {Hader, Christoph},
  title = {simbl: Compressible Similarity Boundary Layer Solver},
  url = {https://github.com/uahypersonics/similarity-bl},
  year = {2026}
}

Validation and Verification

Reproducible VnV cases comparing simbl against independent reference data are in vnv/.

Code Style

This project follows established Python community conventions so that contributors can focus on the physics rather than inventing formatting rules.

Releasing

This project uses Semantic Versioning (vMAJOR.MINOR.PATCH):

• MAJOR (v1.0.0, v2.0.0): Breaking API changes
• MINOR (v0.3.0, v0.4.0): New features, backward-compatible
• PATCH (v0.3.1, v0.3.2): Bug fixes, minor corrections

To publish a new version to PyPI:

1. Verify locally and fix any errors before cutting the release:

   ruff check .
   pytest
   

2. Commit and push to main
3. Tag and push:

   git tag -a vMAJOR.MINOR.PATCH -m "Release vMAJOR.MINOR.PATCH"
   git push origin vMAJOR.MINOR.PATCH