Abstract
A micro-organism is modelled as a squirming sphere with prescribed tangential surface velocity, referred to as a squirmer. The three-dimensional movement of 64 identical squirmers in a simple shear flow field, contained in a cube with periodic boundary conditions, is computed by the Stokesian-dynamics method. In the case of bottom-heavy squirmers, the suspension shows strong non-Newtonian properties. When the background simple shear flow is directed vertically, the apparent viscosity becomes smaller than that of inert spheres. When the shear flow is horizontal and varies with the vertical coordinate, on the other hand, the apparent viscosity becomes larger than that of inert spheres.
