6 research outputs found
Flow curves of colloidal dispersions close to the glass transition: Asymptotic scaling laws in a schematic model of mode coupling theory
The flow curves, viz. the curves of stationary stress under steady shearing,
are obtained close to the glass transition in dense colloidal dispersions using
asymptotic expansions in a schematic model of mode coupling theory. The shear
thinning of the viscosity in fluid states and the yielding of glassy states is
discussed. At the transition between fluid and shear-molten glass, simple and
generalized Herschel-Bulkley laws are derived with power law exponents that can
be computed for different particle interactions from the equilibrium structure
factor.Comment: 14 pages, 14 figures, 4 tables, Eur. Phys. J. E (submitted
A direct numerical simulation method for complex modulus of particle dispersions
We report an extension of the smoothed profile method (SPM)[Y. Nakayama, K.
Kim, and R. Yamamoto, Eur. Phys. J. E {\bf 26}, 361(2008)], a direct numerical
simulation method for calculating the complex modulus of the dispersion of
particles, in which we introduce a temporally oscillatory external force into
the system. The validity of the method was examined by evaluating the storage
and loss moduli of a system composed of identical
spherical particles dispersed in an incompressible Newtonian host fluid at
volume fractions of , 0.41, and 0.51. The moduli were evaluated at
several frequencies of shear flow; the shear flow used here has a zigzag
profile, as is consistent with the usual periodic boundary conditions
Time-dependent flow in arrested states – transient behaviour
The transient behaviour of highly concentrated colloidal liquids and
dynamically arrested states (glasses) under time-dependent shear is reviewed.
This includes both theoretical and experimental studies and comprises the
macroscopic rheological behaviour as well as changes in the structure and
dynamics on a microscopic individual-particle level. The microscopic and
macroscopic levels of the systems are linked by a comprehensive theoretical
framework which is exploited to quantitatively describe these systems while
they are subjected to an arbitrary flow history. Within this framework,
theoretical predictions are compared to experimental data, which were gathered
by rheology and confocal microscopy experiments, and display consistent
results. Particular emphasis is given to (i) switch-on of shear flow during
which the system can liquify, (ii) switch-off of shear flow which might still
leave residual stresses in the system, and (iii) large amplitude oscillatory
shearing. The competition between timescales and the dependence on flow history
leads to novel features in both the rheological response and the microscopic
structure and dynamics.Comment: Review article, 16 pages, 4 figure