Dynamics of suspensions of spherical doublets in simple shear and pressure driven flow

Suspensions of non-spherical particles are commonly encountered in the flow procedures used in material processing industries and biological applications. The rheological properties of these suspensions are influenced by both the dynamics and the orientation of the suspended particles, which is a characteristic that can be affected by hydrodynamic interactions. The rheology and dynamics of a suspension of spherical doublets in bounded flow between plane parallel walls were examined using the Stokesian Dynamics simulation method. The doublets consisted of two rigid spheres connected by inter-particle forces. These doublets are commonly observed in the agglomeration of particles during the processing of suspensions. The simulations were performed for particles undergoing both simple shear and pressure driven flow between two parallel walls. For all concentrations, the viscosity of the suspension of doublets was observed to be higher than the values determined for spherical particles. The wall normal stresses were similar for both types of suspensions. In addition to the shear and normal stresses, the velocity and concentration profiles in simple shear and pressure driven flow in the channel were also studied. In pressure driven flow, the shear induced migration observed with the doublets was similar to the behaviour observed with the spherical particles. Compared with the suspension of spherical particles in pressure driven flow, the maximum centreline concentration for the doublets always exhibited a lower value. An analysis of the orientation parameter indicated that the doublets near the wall were aligned in the flow direction, with the particles in the centre of the channels exhibiting random orientations.