Free · Physics models
Porous Sample Flow and Void Fraction
Estimate intrinsic permeability and pore-volume fraction from pressure-driven flow and residence time.
- Formula & worked example
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Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
Pressure difference (Δp) = 100000.00; Permeability (k) = 101.32500; Porosity (φ) = 0.20000000. The worked example lists its inputs and unit conventions.
k = QμL/(AΔp); φ = Qt/(AL).
Worked example
Enter these known values and leave the other values blank.
- Pressure in
- 200000 Pa
- Pressure out
- 100000 Pa
- Distance (L)
- 1 m
- Area (A)
- 1 m²
- Discharge (Q)
- 0.01 m³/s
- Viscosity (μ)
- 0.001 Pa⋅s
- Residence (t)
- 20 sec
- Pressure difference (Δp)
- 100000 Pa
- Permeability (k)
- 101.32 d
- Porosity (φ)
- 0.2
Assumptions and limitations
- Steady laminar incompressible flow through a uniform sample is assumed. Residence-time porosity is an effective connected pore-volume estimate. The forward-flow pressure difference is positive and void fraction is at most one.
- Clear the quantity to solve an inverse; keep known quantities fixed with locks. Some inverses are singular or ambiguous and require further known values.
- Unit selectors convert the same physical quantity. Rounded reference constants and presets limit physical accuracy even when arithmetic displays more digits.
Common questions
What does this model assume?
Steady laminar incompressible flow through a uniform sample is assumed. Residence-time porosity is an effective connected pore-volume estimate. The forward-flow pressure difference is positive and void fraction is at most one.
Can I solve for an input?
Editable calculated fields support the captured inverse relationships. Clear the unknown and supply enough independent known values; an inverse must remain within the declared physical domain.
References
Enforce the reviewed model domain: Connected pore fraction must exceed zero and cannot exceed one. Intrinsic permeability must be positive.