Jeffrey Morris
CUNY City College, NY·Engineering
Cement, mud, ceramic slurries, molten chocolate and cornstarch in water are all dense suspensions: liquids packed with solid particles. These materials can behave strangely.
- Fields
Engineering
Physics
Materials Science
- Topics
dense suspensions
discontinuous shear thickening
shear jamming
- Grants
- 2 known grants, through Aug 2027
What they work on
- Characterize the particle contact networks that form during discontinuous shear thickening in simulated dense suspensions, across different flow types, solid fractions and particle-size mixtures.
- Apply k-core analysis (which finds tightly connected particle clusters) and persistent homology (which describes the shape of force networks) to link network structure to local rigidity and rigidity percolation.
- Use network measures from persistent homology and k-core analysis to compress large simulation datasets into simpler models of suspension flow that can be tested in applications.
- Measure how particle velocities and rotations are correlated in space and time near shear thickening and shear jamming, using simulations of particles with stress-activated frictional contacts.
- Apply crossover scaling theory to diverging shear and normal stresses near the two jamming points, and build a continuum theory of stress-induced rigidity, including simulations of a probe particle pulled through the suspension.
More about the research
Stir them a little faster and they can suddenly become much thicker, an effect called discontinuous shear thickening (DST). With enough force they can even lock up into a solid, which is called shear jamming. Earlier research suggests one cause. Under strong flow, particles push through the thin liquid film between them and touch, and friction stops them from sliding past one another. A predictive theory is still missing, though, because it is unclear how these contacts between pairs of particles add up to the behavior of the whole material. Both projects use computer simulations of many interacting particles to connect particle-level contacts and motions to how the bulk material flows. Both are collaborative grants shared with partner investigators.
Why it matters
Being able to predict and control when dense suspensions suddenly thicken or jam could help industries that pump and mix cement, ceramics, chocolate and materials for additive manufacturing (3D printing). Engineers could use it to raise or lower flow resistance on purpose. The same understanding may also improve predictions of natural hazards such as mudslides, and could point to mechanical or chemical changes that make materials perform better.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
Closest labs
Xiaoyu Tang
Northeastern University, MA·Engineering·Early-career
Build an experimental platform that combines several advanced diagnostic methods to resolve flow, stress and particle concentration inside complex-fluid droplets as they hit surfaces, including opaque particle suspensions.
Frederick MacKintosh
Rice University, TX·Physics
Develop a predictive effective medium theory, an averaging method that treats the network as a uniform material, for the strain-driven stiffening transition in 2D and 3D networks of stiff, athermal fibers such as collagen.
Yida Zhang
University of Colorado Boulder, CO·Engineering·Early-career
Examine whether self-organization governs how grains in granular soils collectively break under slow, quasi-static loading, and test whether simple universal rules describe crushing in soils with any grain-size mix.
The school
CUNY City College: 9 labs on PI Pages, $72M a year on research, 31 research doctorates a year.
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