Shear thickening and frictional rheology

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Shear thickening is a counter-intuitive phenomenon in which the viscosity of a sheared suspension increases, sometimes by orders of magnitude, for some applied shear stress. We perform particle-level numerical simulations of thickening suspensions focusing on the role of contacts and friction between suspended particles. We also study the relation between thickening and jamming.
Force Chains in a Sheared Dense Suspension

By Ryohei Seto

Inertial flow of suspensions

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The flow of inertial suspensions around a cylindrical object creates a wake zone behind the obstacle. This has been observed experimentally and by simulations. The simulations allow a visualization of the streamlines, which highlights the inertial effects that the particles are subjected to.

Flow of suspension over the obstacles

Simulation method: Lattice-Boltzmann

Visualization: Vpython, Camtasia and iMovie

By Hamed Haddadi

Complex Dynamics of Multiple Particles Released in a Steady State Wake

Simulation method: Lattice-Boltzmann

Visualization: Vpython, Camtasia and iMovie

By Hamed Haddadi

Escape of The Particle From the Wake

Simulation method: Lattice-Boltzmann

Visualization: Vpython, Camtasia and iMovie

By Hamed Haddadi

T-junction

Re = 20

By Sojwal Manorkaar

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Simulation: Finite Element Method using COMSOL(R) Multiphysics

By Omer Sedes

The flow of a dilute suspension at a T - junction geometry at moderate Reynolds numbers. The distribution of particles among the outlet branches is influenced by the interaction of the particles with the detailed flow structure near the junction and also by the migration of the particles due to inertial lift forces at the inlet branch.

Re = 400

By Sojwal Manorkaar

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Simulation: Finite Element Method using COMSOL(R) Multiphysics

By Omer Sedes

Colloidal suspensions

Colloidal suspensions are subject to Brownian motion and the particles interact through hydrodynamics. The particles can also be subject to interparticle forces, be hard-spheres or soft particles. The microstructure formed in a suspension under shear flow depends on the strength of the shear rate and the forces present in the system, and this microstructure has a non-trivial relationship to the macroscopic stress in the suspension. Even for very small particles, experiments show that frictional contacts matter. This also has important consequences on the rheology, and simulations including frictional contacts show a drastically different picture than without.

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Hydrate forming emulsions

Our aim is to investigate the properties of hydrate-forming emulsions and the resulting hydrate slurries using rheology, morphology, interfacial measurements, calorimetry and flow loop. By scanning a wide range of typical subsea oil field conditions experimentally, we have developed morphology maps and flow maps, which provide guidelines for safe and dangerous limits of subsea petroleum pipeline operation leading to better risk management strategies.

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Bimodal suspensions

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Microstructural theory

Most analytical treatments of particle interactions and their resulting configuration operate on a two-particle level. This approximation works well for dilute suspensions, but third-particle interactions need to be included in order to predict the microstructure of the particle suspension. This can be done by modifying the pair-level Smoluchovski equation to form an integro-differential equation that includes a mean-field effect. The correct handling of shear-induced relative diffusion is crucial (the picture on the right shows the relative trajectories of particles in a sheared suspension from simulations).

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By Ehssan Nazockdast