Viscosity (dynamic/absolute viscosity)
Dynamic viscosity and absolute viscosity are synonymous. The symbol for viscosity is the Greek
symbol eta (r|), and dynamic viscosity is also commonly referred to using the Greek symbol
mu (p). The SI physical unit of dynamic viscosity is the pascal-second (Pa-s), which is identical
to 0 kg/(ms) (kilogram per metre-second). If a fluid with a viscosity of one Pa-s is placed
between two plates, and one plate is pushed sideways with a shear stress of one pascal, it
moves a distance equal to the thickness of the layer between the plates in one second.
Kinematic viscosity
In many situations, we are concerned with the ratio of the viscous force to the inertial force, the
latter characterised by the fluid density p. This ratio is characterised by the kinematic
viscosity (v), defined as follows: