Enter the pressure drop, superficial air velocity, and sample thickness into the calculator to determine the flow resistivity.

Flow Resistivity Calculator

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From measurement

Enter your values and click Calculate to get flow resistivity in Pa·s/m².

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Flow Resistivity Formula

The following formula is used to calculate the flow resistivity for a given pressure drop, superficial air velocity, and sample thickness.

\sigma = \frac{\Delta p}{v \cdot T}

Variables:

  • σ is the (specific) airflow resistivity / flow resistivity (Pa·s/m²)
  • Δp is the pressure drop across the sample (Pa)
  • v is the superficial (Darcy) air velocity through the sample (m/s)
  • T is the sample thickness (m)

To calculate the flow resistivity, divide the pressure drop by the product of the superficial air velocity and the sample thickness.

What is Flow Resistivity?

Flow resistivity (often called specific airflow resistivity) is a measure of the resistance to airflow through a porous material. It is an important parameter in acoustics and material science, as it affects the sound absorption and insulation properties of materials. Flow resistivity is typically expressed in units of pascal-seconds per square meter (Pa·s/m²). A higher flow resistivity indicates greater resistance to airflow, which can be beneficial in applications requiring sound insulation or damping.

How to Calculate Flow Resistivity?

The following steps outline how to calculate the Flow Resistivity.

  1. First, determine the pressure drop (Δp) across the material.
  2. Next, measure the superficial air velocity (v) through the material (for example, volumetric flow rate divided by the sample cross-sectional area).
  3. Then, measure the thickness (T) of the sample material.
  4. Finally, calculate the flow resistivity using the formula σ = Δp / (v · T).
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Pressure Drop (Δp) = 100 Pa

Superficial Air Velocity (v) = 0.01 m/s

Sample Thickness (T) = 0.05 m