Carreau-Type Plateaus: A Power Law Cannot Describe Every Shear-Rate Region

Identify the Deformation and Model

COMSOL describes a Carreau viscosity model with low-rate and high-rate viscosity limits and a transition governed by rate-dependent parameters. Those limits differ from an unrestricted mid-range power law. Primary reference: Carreau model boundaries.

Review a Hypothetical Comparison

Suppose a hypothetical fit explicitly assigns low-rate viscosity 10 Pa·s and high-rate viscosity 1 Pa·s. Its limiting viscosity ratio is ten. Those assigned plateaus are model parameters, not proof that measurements reached either region; many transition curves can share these same limits while differing substantially at an intermediate rate.

Keep the Evidence with the Decision

Mark measured points, transition region and extrapolated limits separately on the review plot. Retain the complete Carreau-type equation because added shape parameters or alternative conventions change its interpretation. Ask whether the dataset contains evidence for both plateaus or whether one was merely assumed during fitting. Compare models at the actual proposed rates rather than judging only their fit inside one narrow interval.

Neither finite limits nor an appealing smooth curve establish accuracy outside the supporting material conditions. The invented parameters specify no HM formulation, nozzle rate or permitted viscosity. The decision is whether the proposed extrapolation has a documented asymptotic basis and sufficient evidence, rather than using a middle-section trend as if it described every possible rate.

Does the proposed extrapolation preserve finite low- and high-rate viscosity behavior?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Primary reference: Carreau model boundaries
• Reference from hmpharmamachines.com