Power-law fluid

In the constitutive laws of the rheology (flow law ) is often non-linear approximation approaches are made ​​by power laws in order to also describe the behavior of non-Newtonian fluids can.

The general power law, Herschel - Bulkley relationship also called, is:

With the yield point.

With the parameters we obtain the two-parameter flow law Ostwald de Waele and:

,

Are:

• : Shear stress (see stress ( mechanics) )
• K: Consistency
• : Shear rate
• S: melt index.

The flow index n characterizes the deviation from Newtonian behavior:

• N <1: pseudoplastic ( shear thinning ) or pseudoplastic ( plasticity )
• N = 1: Newtonian
• N> 1: dilatant ( shear thickening ).