Particle stress in suspensions of soft objects

Abstract

In a suspension of extended objects such as colloidal particles, capsules or vesicles, the contribution of particles to the stress is usually evaluated by first determining the stress originating from a single particle (e.g. via integrating the fluid stress over the surface of a particle) and then adding up the contributions of individual particles. While adequate for a computation of the average stress over the entire system, this approach fails to correctly reproduce the local stress. In this work, we propose and validate a variant of the method of planes which overcomes this problem. The method is particularly suited for many-body interactions arising from, for example, shear and bending rigidity of red blood cells.

Local shear stress and its correlation with local volume fraction in concentrated non-Brownian suspensions: Lattice Boltzmann simulation

“…This algorithm has successfully predicted the local stress of a simple liquid, and has been further applied to polymer melts [33]. Recently, it was extended to LBM coupled with the immersed boundary method (IBM) [20]. In this study, we applied the MOP algorithm to the smoothed profile method (SPM) with a slight modification.…”

“…In this study, we applied the MOP algorithm to the smoothed profile method (SPM) with a slight modification. Even in this case, the solvent and particle contributions to total stress can be locally measured at each of the planes along the shear-gradient direction in the same manner as the original algorithm [20].…”

“…(25). In Krüger's work [20], F jx (t) was defined as the x component of the force imposed on the lattice node j at time t, and it could be directly measured by the interfacial tension or the membrane forces on the Lagrangian nodes (for soft particles). In the present SPM system, F jx can be alternatively changed to the x component of the hydrodynamic force f H on a solid particle in Eq.…”

“…To describe the moving wall with velocity u w , the original equation is modified as in Eq. (20), where f * i means the fluid distribution after the collision process, and i denotes the inverse direction of i. The newly added term in the right-hand side of Eq.…”

“…For non-Brownian suspensions, wall shear stress and local shear stress were measured for various particle volume fractions, and they were correlated with locally evolved particle microstructures. To describe non-Brownian suspensions, smoothed profile method (SPM) [19], which was successfully coupled with LBM, was adopted, and the method of planes (MOP) [20] was additionally applied to access the local stress of the suspensions. The paper is organized as follows.…”