Dense bidisperse suspensions under non-homogeneous shear.

Area of Science:

• Fluid dynamics
• Rheology
• Materials science

Background:

• Bidisperse suspensions exhibit complex rheological behavior under shear flow.
• Non-uniform shear flow, a combination of linear shear and sinusoidal disturbance, presents unique challenges in understanding suspension dynamics.

Purpose of the Study:

• To investigate the rheological behavior of three-dimensional bidisperse suspensions under non-uniform shear flow.
• To identify the effects of streamwise disturbances on suspension viscosity and phase distribution.
• To elucidate the physical mechanisms behind phase separation and its impact on rheology.

Main Methods:

• Simulating three-dimensional bidisperse suspensions under superimposed linear shear and sinusoidal flow.
• Analyzing the relative viscosity and particle phase distribution in response to varying disturbance amplitudes and wavenumbers.
• Developing a physical model to explain the observed phase separation phenomenon.

Main Results:

• Streamwise disturbances in the shear plane substantially reduce relative viscosity.
• A threshold amplitude is required for the viscosity reduction effect, while wavenumber dictates the extent of reduction and phase affected.
• Rheological changes are driven by effective phase separation, leading to distinct regions of large and small particles.

Conclusions:

• Phase separation is the key mechanism for rheological modification in bidisperse suspensions under specific non-uniform shear conditions.
• The study provides a physical explanation for triggering phase separation and its impact across the flow curve.
• Understanding these dynamics is crucial for controlling the flow properties of complex fluids.