Engineering calculators / Porous media
Darcy Permeability Calculator
Back-calculate apparent directional permeability from measured liquid flow and media-only differential pressure.
Examples are not product data. Unit changes convert existing values.
Formula and assumptions
u = Q / A; k = μ × L × Q / (A × Δp); R = L / k
For steady, fully saturated, single-phase Newtonian liquid flow with constant viscosity in the linear Darcy regime. Use the gross exposed media area, not net opening area. Excludes inertial losses, compressible gases, gravity head, clogging, bypass, support/interface losses and housing losses. No material presets, rated capacity, service life or filtration efficiency are inferred. Example values are arithmetic examples, not product specifications.
Subtract independently measured fixture and support losses before entering Δp. A single point gives apparent permeability only. Confirm a linear flow–pressure relationship at multiple test points and report fluid, temperature and flow direction. Do not subtract an assumed loss. Very small Δp is sensitive to measurement uncertainty.
Frequently asked questions
Does this identify intrinsic permeability?
Only when the measurement and Darcy assumptions support it. A single result is labeled apparent permeability.
Can I enter total cartridge pressure loss?
Only if the media-only loss has been established. Housing, support and interface losses otherwise bias the result.
Can I use a dry-gas test?
This liquid model does not correct for gas compressibility or slip. Use a validated gas-specific method.
Is porosity enough to calculate permeability?
No. Permeability requires measured data or a validated structural model.
Model reference: COMSOL Darcy’s law equation formulation. Series equations follow from adding each layer’s Darcy pressure drop under the common-area assumptions above.
