ABSTRACT
The shear stress applied to the top plate via the tangential force is r = Ft/A. For Newtonian fluids, it is found that the velocity gradient dv / dx is proportional to the shear stress1, the constant of proportionality being the viscosity of the fluid. Viscosity is thus defined:
A highly viscous fluid is thus one that does not shear rapidly under a large shear stress. Using MKS units, viscosity has units of [kg/(m · s)] or Pascal·seconds2• Viscosity, in older literature, was expressed using the CGS unit "poise" = [g/(cm·s)]; 1 Pa·s = 10 Poise.
