Alignment of particles in sheared viscoelastic fluids

Abstract

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Simulations of flow induced ordering in viscoelastic fluids

“…Periodic boundary conditions effectively turn the row of colloids into an infinitely long string; the intercolloidal spacing of 0.5R g , corresponding to a distance of 2.5R g between the centers of two trailing colloids, is comparable to the gap between colloids in strings of finite length, as studied in our preceding simulations [102]. The critical viscosity, in the range of values studied, is roughly proportional to the friction coefficient, In all cases studied here, the second term between the curly brackets may be ignored, which yields thatγ c is inversely proportional with ξ e and scales approximately with α 1/2 .…”

“…The configurational free energy of a system consisting of long flexible chains in a solvent is well described by the Flory-Huggins (FH) theory [36,51]. We adapt the FH model to calculate the free energy for each chain in a given local configuration of centers of mass [102]. The total free energy is then a sum over the free energies per particle a p , given by…”

“…In Chapter 2 we performed simulations of spherical colloids dispersed in viscoelastic fluids in order to investigate whether we could reproduce the experimentally observed colloidal alignment, or the absence thereof, when these suspensions are subjected to shear flow [102].…”

“…The latter are obtained by changing some of the parameters in the RaPiD simulation model. The range of the parameters is chosen such as to include two particular liquids that were studied in our previous work [102]. We stress that these liquids were tuned to have linear and non-linear rheological properties equal to two liquids that were used experimentally.…”

“…In order to have access to three-dimensional suspensions containing dozens of colloids we recently [102] made use of a particle based model to simulate large amounts of visco-elastic polymer solutions. This model, based on the Responsive Particle Dynamics (RaPiD) method [14,117], allows simulations of thousands of polymers in solutions or in the melt.…”