Simple model for heterogeneous flows of yield stress fluids

Area of Science:

• Rheology and fluid dynamics
• Soft matter physics
• Material science

Background:

• Yield stress fluids exhibit spatial heterogeneities, influencing their flow behavior.
• Understanding these heterogeneities is crucial for predicting fluid response under shear.
• Previous models often simplified or ignored these complex spatial variations.

Purpose of the Study:

• To model the impact of spatial heterogeneities on the flow behavior of yield stress fluids.
• To investigate the influence of nonmonotonic local flow curves on macroscopic properties.
• To analyze the effects of different boundary conditions in simple shear geometries.

Main Methods:

• Development of a simple model incorporating nonmonotonic local flow curves.
• Simulation of simple shear flow with varying boundary conditions.
• Analysis of macroscopic stress-shear rate relationships and flow patterns.

Main Results:

• Homogeneous flow observed in the bulk under controlled macroscopic shear stress.
• Hysteretic macroscopic stress-shear rate curves were found.
• Shear banding predicted under controlled macroscopic shear rate within a specific range.
• Stick-slip behavior observed at small shear rates.

Conclusions:

• The model successfully captures complex flow phenomena like shear banding and stick-slip.
• Macroscopic behaviors are robust to changes in boundary conditions.
• Spatial heterogeneities significantly impact the rheological response of yield stress fluids.