Viscosity is the property of gases and liquids to resist the irreversible movement of one part relative to the other during shear, stretching and other types of deformation.
Dynamic (absolute) viscosity µ is the force acting on the unit area of a flat surface that moves with unit velocity relative to another plane surface located from the first at a unit distance.
In the international system of units (SI), the dynamic viscosity is measured in Pascal-seconds [Pa·s].
There are also non-SI metric units for the measurement of dynamic viscosity. The most widespread in the system GHS - poise [P] and its derivative centipoise [cP].
Also, the dynamic viscosity can be measured in [dyn·s/cm²] and [kgs·s/m²] and the units derived from them.
Correlation between units of dynamic viscosity:
In view of the fact that in some English-speaking countries the strength and surface area can be measured in units other than the SI system, different units of dynamic viscosity can be used.
Kinematic viscosity ν is the ratio of the dynamic viscosity μ to the liquid density ρ and is determined by the formula:
ν = µ / ρ, μ is the dynamic viscosity, Pa · s, ρ is the density of the liquid, kg / m³.
In the international system of units (SI), the kinematic viscosity is measured in square meters per second [m² / s].
Also non-SI metric unit - Stokes [St] and its derivative - centistoke [cSt] are widely used.
Correlation between units of kinematic viscosity:
In view of the fact that in some English-speaking countries the strength and surface area can be measured in units other than the SI system, different units of kinematic viscosity can be used.