In fluid mechanics, a generalized Newtonian fluid is an idealized fluid for which the shear stress is a function of shear rate at the particular time, but not dependent upon the history of deformation. Although this type of fluid is non-Newtonian (i.e. non-linear) in nature, its constitutive equation is a generalised form of the Newtonian fluid. Generalised Newtonian fluids satisfy the following rheological equation:
where is the shear stress, and is the shear rate. The quantity represents an apparent viscosity or effective viscosity as a function of the shear rate.
The most commonly used types of generalized Newtonian fluids are: Power-law fluid Cross fluid Carreau fluid Bingham fluid
It has been shown that lubrication theory may be applied to all generalized Newtonian fluids in both two and three dimensions.
See also Navier–Stokes equations
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