OpenEngine

A Python-based rocket engine nozzle flow simulator. OpenEngine calculates compressible gas flow through a de Laval (Rao-bell) nozzle including wall friction effects, producing detailed flow field data suitable for CFD post-processing and Ansys import.

Features

• Two-stage numerical solver — isentropic ODE (Stage 1) followed by a convergence loop with full friction modelling (Stage 2)
• Rao-bell nozzle geometry — 6-segment profile (circular arc + straight + Bézier curve) parameterised by throat radius and expansion ratio
• Variable gas properties — γ, Cp, Pr, and molar mass specified as 3-node profiles (chamber / throat / exit), PCHIP-interpolated along the nozzle axis
• Interactive GUI — PySide6 dark-themed interface with four tabs: Geometry, Parameters, Simulation, Results
• Live convergence monitor — per-variable L1 residual curves updated in real time during the solve
• Results export
  • CSV with full flow field (Mach, pressure, temperature, adiabatic wall temperature, …)
  • DXF nozzle contour for CAD import
  • 3D wall point cloud CSV for Ansys/CFD mesh generation (with optional full or partial revolve)
• 3D preview — interactive matplotlib 3D scatter plot of the wall point cloud, colour-mapped by any flow property
• JSON parameter files — human-readable configs in params/, editable from the GUI or any text editor
• Desktop launcher — setup_launcher.py creates a Windows shortcut with a custom icon (no console window)

Requirements

Package	Minimum version
Python	3.10
numpy	2.0
scipy	1.10
matplotlib	3.7
PySide6	6.5
ezdxf	1.1
Pillow	10.0 (setup_launcher.py only)

Installation

git clone https://github.com/WiktorBoltrukiewicz/OpenEngine.git
cd OpenEngine
pip install -r requirements.txt

Windows desktop shortcut (optional)

python setup_launcher.py

This converts icon.png to icon.ico and creates OpenEngine.lnk on your Desktop. Requires Pillow (pip install Pillow).

Running

GUI (recommended)

python ui.py

CLI / batch mode

python main.py                        # interactive — select a parameter file
python main.py params/default.json   # load a specific file
python main.py --default             # run with built-in defaults

Parameter Files

Configuration is stored as JSON files in the params/ directory. The included files are:

File	Description
default.json	Baseline rocket engine (hydrogen fuel, 6 MPa chamber pressure)
Liquid_Ethanol_N2O.json	Ethanol / nitrous oxide propellant combination

Each file contains sections for initial conditions, nozzle geometry, gas properties, cooling channels, wall material, coolant properties, and solver settings. Gas properties accept either a scalar (constant along the nozzle) or a 3-element array [chamber, throat, exit] for spatially-varying profiles.

To create a new configuration, copy an existing file and edit the values. The GUI Parameters tab provides an inline editor with units and descriptions for every field.

Output

Simulation results are written to the results/ directory as CSV files. Each run produces a file named after the parameter file (e.g. results/default_results.csv).

Column names follow SI units throughout:

Column	Description
x_m	Axial position [m]
r_m	Nozzle wall radius [m]
M	Mach number [-]
P_Pa	Static pressure [Pa]
T_K	Static temperature [K]
T_aw_K	Adiabatic wall temperature [K]

The Results tab allows interactive plotting of any two columns and exports the wall geometry as a 3D point cloud for CFD use.

License

This project is licensed under the PolyForm Noncommercial License 1.0.0.
Free for personal, educational, research, and non-profit use.
Commercial use requires a separate written agreement.
See LICENSE for full terms.