openflume (Python)

Python API for OpenFLUME, an open-source thermal-fluid network solver for steady and transient analysis of propulsion feed systems, cryogenic lines, and tank pressurization, with real-fluid properties from CoolProp.

pip install openflume            # add [numpy,pandas] for array/DataFrame output

No other installation is needed. The solver core is the same TypeScript code as the web app, bundled into the package and run on a Node.js runtime that pip installs as a dependency (nodejs-wheel-binaries). It is the same solver, with the same verification record, not a port.

Quick start

import openflume as of

net = of.load("feed_system.fn")  # .fn from the web app, or .json
print(net.validate())  # [] means runnable

result = net.solve()  # steady or transient per settings.mode
print(result.converged, result.node("tank")["pressure"])  # SI units: Pa

Start from a bundled example and edit the model as a plain dict:

net = of.example("Tank blowdown")
net.settings["endTime"] = 2.0
net.branch("orifice")["component"]["cd"] = 0.65

tr = net.solve(progress=lambda p: print(f"t = {p['time']:.3f} s", end="\r"))
t, p = tr.times, tr.series("tank", "pressure")  # numpy arrays if numpy is installed
df = tr.frame()  # pandas: index time, columns (id, quantity)

Parameter sweeps are ordinary Python:

base = of.example("Sanity: orifice hand-calc")
for cd in (0.55, 0.60, 0.65):
    net = base.copy()
    net.branch("o")["component"]["cd"] = cd
    print(cd, net.solve().branch("o")["mdot"])

Fluid properties use the same EOS models as the solver:

lox = of.Fluid.real("Oxygen")
lox.density(2e6, 95.0)  # kg/m³
lox.saturation_temperature([1e5, 5e5, 1e6])
of.fluids(curated=True)  # CoolProp HEOS catalogue
of.combustion_gas("lox-rp1", pc=7e6, of=2.6)  # NASA CEA equilibrium tables

Command line:

openflume validate model.fn
openflume solve model.fn -o result.json
openflume info

Notes

• Units are SI throughout: Pa, K, kg/s, m, m², J/kg.
• Always check result.converged. The solver returns its best state either way.
• Model format. Network.config is the NetworkConfig dict (schema v2) defined in src/core/schema.ts and documented in the user manual. .fn files round-trip losslessly with the web app.
• User code. Models can embed JavaScript user components (componentLibrary). That code runs in the Node process with your user's privileges, so only solve models you trust.
• Runtime. One Node process per Session is started on first use and stopped at exit. Set OPENFLUME_NODE to use a specific Node.js 22+ executable. For parallel sweeps, use one process (and therefore one session) per worker, e.g. with concurrent.futures.ProcessPoolExecutor. Ctrl-C interrupts a running solve.

Full documentation: docs/python.md. License: MIT.