Second-order fluid

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A second-order fluid is an extension of the model of a first-order fluid.

It can be written as

\mu_{\operatorname{eff}}(\dot \gamma, T) = \exp \left( A_0 + A_1 \ln(\dot \gamma) + A_2 T + A_3 (\ln(\dot \gamma))^2 + A_4 T \ln(\dot \gamma) + A_5 T^2 \right)

where \dot \gamma is the shear rate, T is temperature and A0 to A5 are coefficients.

The model is more accurate than the first-order fluid, and is one of the basic models used in Moldex3D and Moldflow simulation.