The odd flows of an active chiral annulus

The axisymmetric flow patterns due to the rotation and collapse of an actively driven annular chiral fluid monolayer composed of millions of micron-sized colloidal magnets sitting on a passive subphase are studied. Exact representations for the flow field are given in terms of solutions to a singular integral equation. The effects of odd viscosity (a.k.a. Hall viscosity), an allowed but poorly-understood component of the viscous stress tensor in two-dimensional time reversal symmetry-breaking fluids, on the closure of the hole are investigated. Our work suggests that experimentally measuring the closure time could be a novel method of estimating this elusive parameter.