Input Format

FLINT supports two distinct input paths for defining chemical mechanisms and thermodynamic data, depending on your use case and whether Cantera is available.

Path	Format	Best For	See
YAML	Human-readable	Development, testing, flexibility	YAML Specification
Native	Pre-tabulated	Production, high-performance, no Cantera	Native Format Specification

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YAML Format

Use this if:
- You have Cantera installed
- You're developing or testing mechanisms
- You need to modify reaction rates or species properties
- You want human-readable input files
- You prioritize flexibility over raw speed

Features:
- Single file (.yaml) format
- Complete specification in one place
- Easy to edit and version control
- Full Cantera interoperability

For detailed formulations, see: YAML Specification

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Native Files

Use this if:
- You have a production-validated mechanism
- You need maximum performance (no parsing overhead)
- Cantera is not available or not desired
- You want pre-tabulated data for speed

Features:
- Four to seven pre-computed files (.txt, .dat)
- Fast I/O with pre-tabulated properties
- Production-ready

For detailed formulations, see: Native Format Specification

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Comparison Table

Aspect	YAML	Native
Cantera Required	Yes	No
Human-Editable	Yes	No
Number of Files	1	4/7
File Size	Small	Large
Flexibility	High (modify any parameter)	Low (regenerate from YAML)
Use Case	Development	Production

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File Structure Overview

YAML Format

project/
└── INPUT/
    └── mechanism.yaml          # Complete definition

Native Format

project/
└── INPUT/
    ├── phase.txt               # Species list
    ├── chemistry-info.txt      # Chemistry - Metadata & stoichiometry
    ├── chemistry-Arrhenius.dat # Chemistry - Reaction rates
    ├── chemistry-Troe.dat      # Chemistry - Fall-off parameters (optional)
    ├── chemistry-Lindemann.dat # Chemistry - Fall-off parameters (optional)
    ├── transport.dat           # Transport properties (optional)
    └── thermo.dat              # Thermodynamic properties

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Quick Examples

YAML Example

units:
  energy: cal
  activation-energy: cal/mol

species:
  - name: H2
    composition: {H: 2}
    thermo:
      model: NASA7
      data: [...]
    transport:
      diameter: 2.92
      well-depth: 38.0

reactions:
  - reactants: "H2 + O2"
    products: "2 OH"
    rate-coefficients:
      A: 1.7e13
      b: 0.0
      Ea: 48000.0

Native Example

# phase.txt
ideal-gas phase
H2      2.016000
O2     31.998000
OH     17.007000

# chemistry-Arrhenius.dat (Tecplot format)
TITLE = "Arrhenius data"
VARIABLES = "Temperature", "kf", "kb"
ZONE T=Reaction1
I=15000, F=POINT
1.0  0.0e+00  0.0e+00
2.0  1.5e-30  2.3e-40
...

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