By examining the previous equations that describe the material functions, it becomes clear that the model may involve a relatively large number of parameters. Therefore, it is generally suggested that you select identical algebraic functions for both shear and normal viscosities. This is also the default option.

Very large swelling ratios are sometimes observed. This can be adjusted with an appropriate value of the weighting factor .

When considering non-constant material properties, the power law should be avoided if you expect large regions in which there is no deformation. Indeed, the power law exhibits unbounded values under zero deformation. Instead, functions that exhibit a plateau should be preferred, such as the Bird-Carreau law.

It is recommended that you start a calculation without the additional contribution from the simplified viscoelastic model, and hence define an evolution strategy for the parameter . A ramp function that increases quickly is a good choice.