The aim of this work is the investigation of the magnetorheological behavior, under both simple steadyand oscillatory-shear flow regimes, of fluids composed by micron-sized iron particles (average diameter 930 ± 330 nm) dispersed in silicone oil. Magnetic fields ranging from 279 A/m (0.35 mT) to 1727 A/m (2.17 mT) were applied to the suspensions. The effect of silica nanoparticles as stabilizer...

We examine the angular momentum transport properties of disks composed of macroscopic particles whose velocity dispersions are externally enhanced (“stirred”). Our simple Boltzmann equation model serves as an analogy for unmagnetized fluid disks in which turbulence may be driven by thermal convection. We show that interparticle collisions in particle disks play the same role as fluctuating pres...

We discuss sets of measures with the goal of describing dynamical properties of force networks in dense particulate systems. The presented approach is based on persistent homology and allows for extracting precise, quantitative measures that describe the evolution of geometric features of the interparticle forces, without necessarily considering the details related to individual contacts betwee...

A micromechanical study is made of the relationship between interparticle friction coefficient and macroscopic continuum friction and dissipation in idealised granular materials, using Discrete Element Method simulations with varying . As expected, macroscopic friction and dilatancy increase with . Surprisingly, dissipation is present even when or when . Hence, dissipation in idealised granular...

We present results from an independent analysis of friction that more generally addresses all crystalline materials by an extension of coincident site lattice theory and dislocation drag. Calculations for graphitic friction are carried out and agree in magnitude with experimental friction forces. More interestingly, static, dynamic and anisotropic friction forces, incommensurability effects and...

We measure the vibrational modes and particle dynamics of quasi-two-dimensional colloidal glasses as a function of interparticle interaction strength. The interparticle attractions are controlled via a temperature-tunable depletion interaction. Specifically, the interparticle attraction energy is increased gradually from a very small value (nearly hard-sphere) to moderate strength (∼4k_{B}T), a...

We demonstrate a novel approach to quantify the interparticle distance in colloidal dimers using Mie scattering. The interparticle distance is varied in a controlled way by changing the ionic strength of the solution and the magnetic attraction between the particles. The measured scaling behavior is interpreted using an energy-distance model that includes the repulsive electrostatic and attract...

In the discrete element simulation of granular materials, the modelling of contacts is crucial for the prediction of the macroscopic material behaviour. From the tribological point of view, friction at contacts needs to be modelled carefully, as it depends on several factors, e.g. contact normal load or temperature to name only two. In discrete element method (DEM) simulations the usage of Coul...

Here, we calculate the electric forces acting on charged dielectric colloidal particles, which are attached to the interface between a nonpolar fluid (air and oil) and water in the presence of applied uniform external electric field, E0, directed normal to the interface. Electric charges are present on the particle-nonpolar fluid interface. The solution to the problem represents a superposition...