Kinematic viscosity/ momentum diffusivity:

Kinematic viscosity/ momentum diffusivity:

It is defined as the ratio of dynamic viscosity to the density of the fluid.

Kinematic viscosity

ν = μ / ρ
where
ν = kinematic viscosity (m²/s)
μ = absolute or dynamic viscosity (N s/m²)
ρ = density (kg/m³)

In the SI-system the theoretical unit of kinematic viscosity is m²/s - or the commonly used Stoke (St) where

1 St (Stokes) = 10^-4 m²/s = 1 cm²/s

Stoke comes from the CGS (Centimetre Gram Second) unit system.

Since the Stoke is a large unit it is often divided by 100 into the smaller unit centiStoke (cSt) - where

1 St = 100 cSt
1 cSt (centiStoke) = 10^-6 m²/s = 1 mm²/s
1 m²/s = 10⁶ centiStokes

Comments

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