Abstract
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.
Highlights
Mixing of fluids is a two-stage process composed of diffusion overlaid on top of mechanical stirring[1]
We focus on geometries that eliminate direct fluid collisions with the bounding walls in order to reduce mechanical damage to the mixture constituents and geometries that avoid formation of stagnant fluid zones so that any debris can be washed out by the stream
We begin by defining the reference flow which we shall use to demonstrate that chaotic state is produced with less energy expenditures than those required to maintain the unmodified flow
Summary
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. We report here the existence of flow systems where small geometry modifications create bifurcations resulting in a natural creation to new, chaos-capable states These configurations are energetically efficient, i.e., maintaining the new flow either requires less energy than the reference flow or the energy consumption increases at a marginal rate. We focus on geometries that eliminate direct fluid collisions with the bounding walls in order to reduce mechanical damage to the mixture constituents and geometries that avoid formation of stagnant fluid zones so that any debris can be washed out by the stream This leads us to analyze conduits with longitudinal grooves, which we divide into symmetry preserving grooves and symmetry breaking grooves. We demonstrate that separate stirring zones can be created in the former case without introducing any physical barriers
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