These are strictly non-Newtonian, but once the flow starts they behave essentially as NewtonianВ fluids (i.e. viscosity is independent of the rate of shear).ДЄn exception to the rule is Bingham plastics, which are fluids that require a minimum stress to be applied before they flow. This means that the viscosity of Newtonian fluids will remain a constant (see Figure 2) no matter how fast they are forced to flow through a pipe or channel (i.e. As a result, if we look at a plot of shear stressВ versus shear rate (See Figure 1) we can see a linear increaseВ in stress with increasing shear rates, where the slope is given by the viscosity of the fluid. For those fluids viscosity is only dependent on temperature. Some examples of Newtonian fluids include water, organic solvents, and honey. This relationship is now known as Newton's Law of Viscosity, where the proportionality constant О· is theВ viscosity of the fluid: Newtonian fluids are named after Sir Issac Newton (1642 - 1726) who described the flow behavior ofВ fluids withВ a simple linear relation between shear stress and shear rate. Each unique material has its own behavior when subjected to flow, deformation or stress.Дepending on their viscosity behavior as a function of shear rate, stress, deformation history., fluids are characterized as Newtonian or non-Newtonian. However,В fluid characterization is far more deep and complex than what is usually expected.

If you are on this site, you probably have a general idea aboutВ what is viscosity and how important it isВ in the development of any application that involvesВ fluid flow. Viscosity of Newtonian and non-Newtonian Fluids

Absolute viscosity