ABSTRACT
An external stress applied to a portion of a fluid, as illustrated in Figure 10.1, will introduce a movement of the molecules of the affected part of the fluid in the direction of the applied stress. The moving molecules will interact with the neighboring molecules, which will start moving too, but with a lower velocity than that of the molecules exposed to the stress. The dynamic viscosity,
η
, is defined as
(10.1)
where
τ
=
applied shear stress (force per area unit
=
F/A), v
=
velocity of fluid in x-direction, and
=
shear rate.
