Kinematic Viscosity Formula
Kinematic viscosity is the measure of the inherent resistance of a fluid to flow when no external force is exerted, except gravity. It is the ratio of the dynamic viscosity to its density, a force independent quantity. Kinematic viscosity can be obtained by dividing the absolute viscosity of a fluid with the fluid mass density.
Kinematic viscosity = Dynamic viscosity / Fluid mass density
The equation is written
ν = η / ρ
ν: Kinematic viscosity
ρ: fluid density
η: Dynamic viscosity
Kinematic Viscosity Formula Questions:
1) In a liter of mercury that weights 2 Kg, what is its kinematic viscosity?
Answer: The dynamic viscosity of mercury is η= 1.526 Pa*s. First calculate the density mass of mercury using the formula ρ = mass/volume.
ρ = 2 Kg/ 1 L = 2 Kg/ 0.001 m3 = 2000 Kg/m3
Then calculate the kinematic viscosity using its formula,
ν = η / ρ
ν = 1.526 Pa*s / 2000 Kg/m3 = (1.526 N*s/m2) / (2000 Kg/m3)
ν = 0.000763 m2/s
2) what is the density of a fluid that has a kinematic viscosity of 1 m2/s and a dynamic viscosity of 0.018 Pa*s?
Answer: From the formula of kinematic viscosity we can find the density,
ρ = η / ν and then substituting the values,
ρ = (0.018 N*s/m2) / (1 m2/s) = 0.018 Kg / m3