A nonequilibrium thermodynamics perspective of thixotropy

Area of Science:

• Rheology
• Soft Matter Physics
• Thermodynamics

Background:

• Elasto-viscoplastic fluids exhibit complex behaviors like thixotropy.
• Existing models often rely on empirical equations (e.g., Bingham, Herschel-Bulkley).
• A unified, thermodynamically consistent approach is needed to describe these fluids.

Purpose of the Study:

• To develop a general, thermodynamically consistent elasto-viscoplastic model.
• To integrate thixotropy directly with internal viscoelasticity and network structures.
• To accurately predict rheological data across various conditions.

Main Methods:

• Application of non-equilibrium thermodynamics.
• Derivation of a thermodynamically admissible elasto-viscoplastic model.
• Validation against experimental rheological data.

Main Results:

• The derived model self-consistently incorporates thixotropic effects.
• It accurately reproduces experimental data at both low and high shear rates.
• Predictions show excellent agreement with steady-state and time-dependent rheological data for soft colloidal pastes and blood.

Conclusions:

• The proposed model offers a comprehensive description of elasto-viscoplastic fluids.
• It successfully captures yield stress and thixotropic hysteresis.
• This approach enhances the understanding of thixotropic fluid behavior.