We present an enhancement of diffusive mixing on a compact Riemannian manifold by a fast incompressible flow.
We describe the class of flows that make the deviation of the solution from its average arbitrarily small in an arbitrarily short time, provided that the flow amplitude is large enough.
The necessary and sufficient condition on such flows is expressed naturally in terms of the spectral properties of the dynamical system associated with the flow.
Further studies are needed for non-compact manifolds, or compact manifolds with Dirichlet BC. The optimal shape of the fixed obstacles in the mixing device could be obtained through such a research