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Pyrolysis.jl

A Julia package for simulating thermal decomposition (pyrolysis) of materials under high heat flux. Pyrolysis.jl uses an Arbitrary Lagrangian–Eulerian (ALE) finite-volume discretisation with adaptive meshing, Arrhenius kinetics, in-depth radiation absorption, and pressure-driven gas transport (Darcy–Fick).

Features

  • Multi-component materials with temperature-dependent properties
  • Single-step and multi-step Arrhenius decomposition kinetics
  • Gas generation and transport through porous char (Fickian or Darcy–Fick)
  • In-depth radiation absorption via Beer–Lambert (or surface absorption)
  • Material volume changes — shrinkage, swelling, intumescence
  • ALE mesh motion with surface regression and internal interface tracking
  • Adaptive mesh refinement (h- and r-adaptivity)
  • Operator-based Structured Jacobian with selectable solve strategies, a dense AD verifier, and pluggable linear solvers
  • Runtime mass- and energy-conservation diagnostics
  • Pluggable extensions for Plots recipes, SciML sensitivities, and symbolic-derivative verification

Installation

using Pkg
Pkg.add(url = "https://github.com/GraysonBellamy/Pyrolysis.jl")

Pyrolysis.jl requires Julia 1.10 or newer.

Quick start

using Pyrolysis

pmma = Material(
    name = :PMMA,
    components = (
        SolidComponent(:virgin, ρ = 1190, c = 1420, k = 0.21, ε = 0.86),
        GaseousComponent(:MMA, M = 0.100, c = 1500, k = 0.02, λ = 1e-5),
    ),
    reactions = (
        Reaction(:decomposition, :virgin => :MMA;
                 A = 8.5e12, E = 188e3, h = -870e3),
    ),
)

mesh = create_uniform_mesh(0.01, 100, Val(2))
bcs  = BoundaryConditionSet(
    thermal = (top = HeatFluxBC(50e3), bottom = AdiabaticBC()),
)

problem = PyrolysisProblem(
    mesh = mesh, material = pmma, bc_set = bcs,
    T_initial = z -> 300.0,
    ξ_initial = [z -> 1190.0, z -> 0.0],
    tspan = (0.0, 100.0),
)

sol = solve(problem; progress = false, use_ale = true,
            radiation_model = SURFACE_ABSORPTION)

# Plot recipes (load `Plots` first)
using Plots
plot(sol)                     # surface temperature trace
plot(sol; kind = :heatmap)    # T(z, t) heatmap
plot(sol; kind = :mlr)        # mass-loss rate
plot(sol; kind = :residual)   # energy-conservation residual

The quick-start tutorial walks through every line of a run like this one.

How the documentation is organised

  • User Guide — how to use the package: defining materials, reactions, boundary conditions, and meshes; building and solving problems; post-processing, adaptivity, parameter sweeps, sensitivity analysis, and troubleshooting.
  • Technical Reference — the model itself: governing equations, constitutive closures, discretisation, ALE framework, Jacobian architecture, conservation diagnostics, and verification/validation — with systematic comparisons to ThermaKin2Ds, Gpyro, and the FDS solid-phase model.
  • Examples — end-to-end studies (cone calorimeter, Douglas fir, pressure-treated wood, inverse analysis, sensitivity) shipped in the repository.
  • API Reference — docstrings for the exported surface, organised by area.
  • Development — tests, quality tooling, benchmarks, and how these docs are built.