Simulation of mixing in unsteady flow through a periodically obstructed channel

Abstract

Fluid mixing in steady and unsteady flow through a channel containing periodic square obstructions has been studied using a finite-difference simulation to determine fluid velocities, followed by the use of passive marker particle advection to look at fluid transport out of the cavities formed between each of the obstructions. The geometry and flow conditions were chosen from the work by Perkins (1989, M.S. Thesis, Lehigh University; 1992, Ph.D. Thesis, Lehigh University); who investigated heat transfer enhancement due to unsteady flow through such an obstructed channel. Particle advection shows that flow regimes which are predicted to give good mixing based on snapshots of instantaneous streamline contour plots were not necessarily able to efficiently mix fluid which started in the cavity regions throughout the channel. The use of Poincaré sections shows regular regions existing under these conditions which inhibit efficient fluid transport. These regular regions are found to disappear when the unsteady flow velocity is increased.