Shear rate terms Links

In the case of non-Newtonian fluids the viscosity fi - inclusively that obeying the so-called power law - represents a local quantity, linking the local shear stress r and the local shear rate y acording to r = fty. The term effective viscosity stresses these facts. 

The two models discussed so far are just extensions of the Newtonian constitutive model and thus formulated in terms of shear rate. A proper formulation of strain is needed to fix the frame invariance problem. This question is closely linked to the types of derivatives that are permitted in the constitutive equations. 

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