Hagen number

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The Hagen number is a dimensionless number used in forced flow calculations. It is the forced flow equivalent of the Grashof number.

It is defined as:

where:

• is the pressure gradient
• L is a characteristic length
• ρ is the fluid density
• ν is the kinematic viscosity

For natural convection

and so the Hagen number then coincides with the Grashof number.

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