powerLawRecommended
+ Any exponent is possible
+ Compact formula
- Always isotropic
- C0 depends on zone thickness
Tools
OpenFOAM Porosity Calculator
Calculate porous-media coefficients for powerLaw, DarcyForchheimer, and porousBafflePressure setups from open area, zeta, pressure drop, or two measurement points.
Zeta
1.00
ζ [-]
Pressure Drop
0.60
Pa
powerLaw C0
1.00
[-]
powerLaw C1
2.00
Exponent
Darcy D
0
1/m2
Forchheimer F
2.00
1/m
Pressure-Drop Curve
DarcyForchheimerRecommended
+ Directional resistance
+ Viscous and inertial terms
- Only linear plus quadratic behavior
- D and F depend on zone thickness
OpenFOAM Code
Model Selection
| Situation | powerLaw | DarcyForchheimer | porousBaffle |
|---|---|---|---|
| Thin grille, screen, or filter | - | OK | Best |
| Thick porous medium, foam, or packing | OK | Best | - |
| Directional resistance | No | Yes | No |
| Exponent other than 1 or 2 | Yes | No | No |
| Known zeta value | Convert | Convert | Direct |
| Viscous resistance is important | No | Yes, with D | Yes, with D |
Formula Reference
powerLaw
S = -rho * C0 * |U|^(C1-1) * UC0 = Δp / (ρ * UrefC1 * L)
For C1 = 2: C0 = ζ / (2 * L)
DarcyForchheimer
S = -(mu * D + 0.5 * rho * |U| * F) * UD = Darcy coefficient [1/m2] = 1/K
F = Forchheimer coefficient [1/m]