Streamings in confined active viscoelastic fluids

Confined active matter systems exhibit rich ordering phenomena. A well-known example is bacterial active fluids, which can be stabilized from mesoscale turbulence to a mesoscale spiral vortex when confined. By adding viscoelastic polymers into bacterial active fluids, we previously found that such active viscoelastic fluids would display spatial and temporal ordering at macroscopic scales. Here we study how confinement geometry influences the behavior of viscoelastic bacterial active fluids. We found circulatory streaming in channel-like confinement that resembles biological cytoplasmic streaming with indifferent zones. The findings provide new insight into the control of active matter flows in artificial and biological settings.