Kinematic viscosity, specifically, is a measure of a fluid's internal friction, indicating how easily it flows under the influence of gravity. It is defined as the ratio of the dynamic viscosity ( μ) over the density of the fluid ( ρ) and is commonly denoted by the Greek letter nu (ν). The formula for kinematic viscosity (ν) is given by: ν = μ / ρ
A conversion from absolute to kinematic viscosity in Imperial units can be expressed as γ = specific weight (lb/ft3 ) The viscosity of a fluid is highly temperature dependent - and for dynamic or kinematic viscosity to be meaningful the reference temperature must be quoted. In ISO 8217 the reference temperature for a residual fluid is 100 oC .
Viscosity conversions are based on fluids with specific gravity of one. At temperatures other than 100 or 210°F, convert kinematic viscosity to Saybolt Universal viscosity with U t = U 100°F (1 + 0.000061 (t - 100)) (1) where U t = Saybolt Second Universal (SSU) viscosity at temperature t (°F)