Pipe Wall Shear Stress Calculator

Calculate average wall shear stress in fully developed pipe flow using Darcy friction factor.

τw = fρv² / 8

Darcy friction factor f

Density ρ (kg/m³)

Mean velocity v (m/s)

Enter valid values in all required fields.

What this formula means

Wall shear stress is the tangential force per unit wall area produced by viscous momentum transfer. For fully developed circular-pipe flow it relates directly to the Darcy friction factor and mean velocity.

Use wall shear in pipeline design, erosion checks, sediment transport, biofilm studies, and fluid-processing equipment. The result should be interpreted with consistent units and with the assumptions of the underlying model in mind.

Worked example

With f = 0.02, water density 1000 kg/m³, and v = 3 m/s, τw = 22.5 Pa.

Applications

Use wall shear in pipeline design, erosion checks, sediment transport, biofilm studies, and fluid-processing equipment. It is also useful as an independent check when comparing hand calculations, laboratory measurements, simulations, or preliminary engineering estimates.

Assumptions and common mistakes

Important: Do not confuse Darcy and Fanning friction factors. The Fanning factor is one quarter of the Darcy factor.

Use SI units unless the field label states otherwise. Keep significant figures appropriate to the accuracy of the inputs, and do not treat a simplified calculator as a replacement for codes, detailed design standards, or professional review.

Frequently asked questions

What equation does this calculator use?τw = fρv² / 8. The calculator evaluates the displayed relationship using the values entered above.

Are the results unit-sensitive?Yes. The input labels use SI units so the displayed output follows the corresponding SI unit.

Can I use this for engineering design?Use it for learning and preliminary checks. Final designs require validated data, applicable standards, safety factors, and professional judgment.