Systematic coarse graining flowing polymer melts: thermodynamically guided simulations and resulting constitutive...

Area of Science:

• Rheology
• Polymer Physics
• Soft Matter Science

Background:

• Complex fluids exhibit viscoelasticity due to flow-induced structural changes.
• Microscopic models are essential for understanding fluid dynamics but are computationally intensive.
• Deriving macroscopic constitutive equations from microscopic principles remains a challenge.

Purpose of the Study:

• To develop a systematic coarse-graining method for deriving thermodynamically consistent constitutive equations for complex fluids.
• To enable multiscale simulations bridging microscopic and macroscopic fluid behaviors.
• To accurately predict the rheological properties of complex fluids under various flow conditions.

Main Methods:

• A systematic coarse-graining approach starting from microscopic fluid models.
• Thermodynamically guided simulations within a consistent coarse-graining framework.
• Reconstruction of building blocks for the coarse-grained model.

Main Results:

• Closed-form, thermodynamically consistent constitutive equations were derived.
• The method was validated for low-molecular polymer melts under shear and elongational flows.
• Predicted rheological behaviors, including shear thinning, normal stress differences, and elongational viscosities, matched reference results.

Conclusions:

• The presented coarse-graining method provides a robust framework for modeling complex fluid rheology.
• This multiscale simulation approach accurately captures essential viscoelastic phenomena.
• The derived constitutive equations offer a powerful tool for predicting fluid behavior in various applications.