  T. Borrvall and J. Petersson [Topology optimization of fluids in Stokes flow,
International Journal for Numerical Methods in Fluids 41 (1) (2003) 77--107]
developed the first model for topology optimization of fluids in Stokes flow.
They proved the existence of minimizers in the infinite-dimensional setting and
showed that a suitably chosen finite element method will converge in a weak(-*)
sense to an unspecified solution. In this work, we prove novel regularity
results and extend their numerical analysis. In particular, given an isolated
local minimizer to the infinite-dimensional problem, we show that there exists
a sequence of finite element solutions, satisfying necessary first-order
optimality conditions, that strongly converges to it. We also provide the first
numerical investigation into convergence rates.
