Use of Surface Corrugations for Energy-Efficient Chaotic Stirring in Low Reynolds Number Flows.

We demonstrate that an intensive stirring can be achieved in laminar channel flows in a passive manner by utilizing the recently discovered instability waves which lead to chaotic particle movements. The stirring is suitable for mixtures made of delicate constituents prone to mechanical damage, such as bacteria and DNA samples, as collisions between the stream and both the bounding walls as well as mechanical mixing devices are avoided. Debris accumulation is prevented as no stagnant fluid zones are formed. Groove symmetries can be used to limit stirring to selected parts of the flow domain. The energy cost of flows with such stirring is either smaller or marginally larger than the energy cost of flows through smooth channels.