Chaotic mixing caused by an axially periodic steady flow in a partitioned-pipe mixer

The chaotic mixing of a fluid due to a steady creeping flow in a partitioned-pipe mixer, composed of axially periodic pairs of plane plates within an infinitely long cylinder, is studied. This flow, caused by both the rotation of the cylinder and the axial pressure gradient, has reverse-flow regions unless the rotation is sufficiently small, unlike the approximate flows used in preceding studies. The dependences of the location and size of the islands in the Poincaré section based on the flow of the present study on the parameters of the system are similar to those based on the approximate flows, in spite of the differences between these flows. Moreover, we find that the stretching of fluid elements after their separation by the leading edges of the plates mainly contributes to the mixing, and that fluid elements that are stretched strongly move more slowly in the axial direction than those stretched weakly.