Carreau fluid is a type of generalized Newtonian fluid where viscosity, , depends upon the shear rate, , by the following equation:
Where: , , and are material coefficients.
= viscosity at zero shear rate (Pa.s)
= viscosity at infinite shear rate (Pa.s)
= relaxation time (s)
= power index
At low shear rate () a Carreau fluid behaves as a Newtonian fluid with viscosity . At intermediate shear rates (), a Carreau fluid behaves as a Power-law fluid. At high shear rate, which depends on the power index and the infinite shear-rate viscosity , a Carreau fluid behaves as a Newtonian fluid again with viscosity .
The model was first proposed by Pierre Carreau.