Overview

First public release of the SymPy Nozzle Gasdynamics Lab –
a small symbolic/numeric playground for quasi-1D isentropic nozzle flow.

This version is intended as a compact teaching and exploration tool for:

• students learning compressible flow;
• engineers who want quick SymPy-based isentropic relations;
• researchers who like to prototype ideas in symbolic form
  before going to full CFD.

The project sits between a textbook, a lab notebook, and a Python library.

Added

#### Symbolic core

• src/symgas/symbolic_nozzle.py:
  • isentropic temperature ratio T/T0(M),
  • pressure ratio p/p0(M),
  • density ratio rho/rho0(M),
  • area–Mach relation A/A*(M),
  • helper expressions_for_gamma(...) for a fixed gamma (e.g. 1.4 for air).

#### Numeric wrapper

• src/symgas/numerics.py:
  • IsentropicNozzleNumeric class that turns SymPy expressions into NumPy functions;
  • dimensional_profiles(...):
    • given a Mach profile M(x) and stagnation conditions T0, p0 (and optional rho0),
      returns dimensional profiles T(x), p(x), rho(x), A(x)/A*.

#### Plots

• src/symgas/plots.py:
  • plot_mach_profile(...) – Mach vs station;
  • plot_pressure_temperature_profiles(...) – pressure and temperature on the same axis.

#### Notebooks

• notebooks/01_symbolic_derivations.ipynb
  Step-by-step symbolic derivations for gamma = 1.4:
  T/T0(M), p/p0(M), rho/rho0(M), A/A*(M).

• notebooks/02_nozzle_profiles.ipynb
  Example 1D nozzle profile:

  • prescribed Mach distribution from subsonic inlet
    through a sonic throat to a supersonic exit;
  • computed dimensional T(x), p(x) and plots.

#### Documentation

• docs/Overview_EN.md – conceptual English overview
  (nozzle as organ and as a collider-like channel).
• docs/Overview_RU.md – Russian counterpart with the same idea.
• Updated README.md:
  • project structure,
  • installation instructions,
  • symbolic and numeric usage examples,
  • brief roadmap.

#### Tests and tooling

• tests/test_symbolic_nozzle.py:

  • checks isentropic ratios at M → 0,
  • verifies A/A*(M=1) ≈ 1,
  • validates expressions_for_gamma(...) against direct formulas.

• tests/test_numerics.py:

  • verifies that for M = 0 dimensional profiles tend to T0, p0, rho0;
  • checks monotonic pressure decrease for an increasing Mach sequence
    M = [0.2, 0.5, 1.0, 2.0];
  • confirms that A/A* has a minimum at M = 1 and is > 1 for both
    subsonic and supersonic points.

• CHANGELOG.md – initial changelog entry for v0.1.0.

• pyproject.toml – minimal packaging config (symgas package, src-layout).

• requirements.txt, requirements-dev.txt, pytest.ini, .gitignore.

### Usage

Basic workflow:

# install dependencies
pip install -r requirements.txt

# optional: editable install of the symgas package
pip install -e .

# run tests
pip install -r requirements-dev.txt
pytest

For exploration, open the notebooks:

notebooks/01_symbolic_derivations.ipynb

notebooks/02_nozzle_profiles.ipynb

### Notes and roadmap

This is a prototype lab, not a full nozzle design tool.

Planned directions for future versions:

helpers for subsonic/supersonic branches of A/A*(M);

simple nozzle geometries x → A(x) and corresponding Mach distributions;

basic loss models (non-ideal expansion, friction);

more detailed teaching notebooks for students and self-study.