Effect of diffusion on residence time distribution in chaotic channel flow

We consider the residence time distribution (RTD) of a liquid flowing through a spatially periodic channel. It is shown that chaotic advection significantly reduces deviation of the RTD which then consist of two parts: the main pulse which does not depend on the Péclet number and a long tail which is formed in the near-boundary layer, where the advection is weak. Boundary layer approximation provides the dependence of the statistical moments of the RTD on Péclet number. It is shown that the length of the tail increases with Pe, while its mass decreases. The numerical results support the theoretical findings.