Inertial effects on chaotic advection and mixing in a 2D cavity flow

The mechanisms underlying chaotic advection and mixing in inertial flow at Reynolds numbers above the Stokes flow regime are incompletely understood. This paper describes numerical investigations of chaotic advection and mixing for time-periodic inertial flow in a two-dimensional rectangular cavity driven by alternating motion of the upper and lower walls. The effects of inertia are analyzed in terms of the flow topology and tracer dynamics. The periodic unsteady high Reynolds number laminar flow results in the evolution of the Poincaré map as the Reynolds number increases. Periodic points shift in position from their original locations in Stokes flow, and the Poincaré sections transition from those characteristic of Stokes flow to a different characteristic pattern at higher Reynolds numbers. Tracer motion exhibits increasing degrees of disorder with increasing Reynolds number and decreasing forcing frequency resulting in increased chaotic mixing. The forcing frequency has a much greater impact on chaotic advection and mixing than inertial effects.