Fluctuating lattice-Boltzmann model for complex fluids

Abstract

We develop and test numerically a lattice-Boltzmann (LB) model for nonideal fluids that incorporates thermal fluctuations. The fluid model is a momentum-conserving thermostat, for which we demonstrate how the temperature can be made equal at all length scales present in the system by having noise both locally in the stress tensor and by shaking the whole system in accord with the local temperature. The validity of the model is extended to a broad range of sound velocities. Our model features a consistent coupling scheme between the fluid and solid molecular dynamics objects, allowing us to use the LB fluid as a heat bath for solutes evolving in time without external Langevin noise added to the solute. This property expands the applicability of LB models to dense, strongly correlated systems with thermal fluctuations and potentially nonideal equations of state. Tests on the fluid itself and on static and dynamic properties of a coarse-grained polymer chain under strong hydrodynamic interactions are used to benchmark the model. The model produces results for singlechain diffusion that are in quantitative agreement with theory.

One- and two-particle dynamics in microfluidic T-junctions

“…In this Rapid Communication, our aim is to map out the single-and two-particle dynamics in asymmetric T-junctions using a recently developed lattice-Boltzmann-based simulation technique for extended solid and porous particles [15][16][17]. We first demonstrate that our model agrees quantitatively with experiments [9] in terms of the outlet distributions of fluid and impermeable, solid particles in a T-junction.…”

“…(1) numerically instead. Our model [15][16][17] reproduces the compressible Navier-Stokes equations [27,28] with DBB-like forces, and we have validated it against theoretical results [15]. Here, we use the shear viscosity η = 0.01 g cm −1 s −1 and density of water, ρ = 1 g cm −3 .…”

“…Our porous shell is represented by a rigid surface triangulated with N nodes (Fig. 1 inset), which couple to the LB fluid through local interpolation [15][16][17]29]. Importantly, γ and N are calibrated to values that guarantee consistency between different measurements of the particle's hydrodynamic radius for a given degree of porosity [15,17].…”

Progress in particle-based multiscale and hybrid methods for flow applications

“…Thus, in comparison with a full molecular or multiscale approach, even more computational savings are to be expected while extending the capability of the solver to handle polymeric effects. Ollila et al (2011) mentioned that for thermal fluctuations to be present, the density needs to fluctuate as well. Using a squared speed of sound (as, for example, in Ladd 1994a) will zero out the viscosity which is relevant for fluctuating density flows.…”

Shape and scale dependent diffusivity of colloidal nanoclusters and aggregates

“…Periodic boundary conditions give rise to finite-size effects due to the hydrodynamic interactions. 14,38,[43][44][45][46] They are quantified to first-order using…”