Object transport by a confined active suspension

Numerical simulations in two space dimensions are used to examine the dynamics, transport and equilibrium behaviours of a neutrally buoyant circular object immersed an active suspension within larger container. The continuum model Gao et al. ( Phys. Rev. Fluids , vol. 2, issue 9, 2017, 093302) represents non-interacting, immotile, extensor-type microscopic agents that have direction strength, align response strain rate. Such is well known be unstable above activity strength threshold, which depends upon length scale confinement. Introducing leads additional phenomenology. It can confine fluid between it container wall, suppresses local activity. However, its motion also correlates rates near surface, induce correspondingly correlated active-stress response. Depending on these mechanisms lead either attraction toward or repulsion away from wall. In addition, persistent propagating behaviour found for modest provides mechanism long-range transport. When so weak mobility essential support instability sustain flow, all flow terminates when diminished as nears If scheduled time, then could perform relatively complex tasks with simple agents.