Pressure-driven suspension flow near jamming.

Area of Science:

• Rheology
• Fluid Dynamics
• Materials Science

Background:

• Understanding the flow behavior of dense suspensions is crucial in various industrial applications.
• Previous studies have primarily focused on suspensions with lower solid volume fractions.
• Dense suspensions exhibit complex flow dynamics and jamming phenomena.

Purpose of the Study:

• To investigate the flow behavior and particle distribution of dense suspensions using magnetic resonance imaging.
• To characterize the jamming transition and compaction phenomena in dense suspensions.
• To evaluate the applicability of frictional rheology models for dense suspension flow.

Main Methods:

• Magnetic resonance imaging (MRI) was employed to measure particle volume fraction and velocity profiles.
• Experiments were conducted on suspensions with bulk solid volume fractions up to 0.55 flowing in a pipe.
• Data analysis focused on spatial distributions across the pipe at different axial positions.

Main Results:

• Dense suspensions (ϕ_{0}>0.5) display distinct behavior compared to less concentrated suspensions.
• Experimental results demonstrate particle compaction within the jammed region, from the jamming limit (ϕ_{m}≈0.58) to random close packing (ϕ_{rcp}≈0.64).
• Particle volume fraction and velocity profiles were accurately predicted by a frictional rheology model.

Conclusions:

• Dense suspensions exhibit unique compaction and jamming behaviors not observed at lower concentrations.
• Frictional rheology models, incorporating compaction and normal stress differences, can effectively describe the flow of dense suspensions.
• This study provides valuable insights into the fundamental physics of dense granular flows.