SIMULATION OF MIXING IN UNSTEADY-FLOW THROUGH A PERIODICALLY OBSTRUCTED CHANNEL

Fluid mixing in steady and unsteady Bow through a channel containing p eriodic square obstructions has been studied using a finite-difference simulation to determine fluid velocities, followed by the use of pass ive marker particle advection to look at fluid transport out of the ca vities formed between each of the obstructions. The geometry and Bow c onditions were chosen from the work by Perkins (1989, M.S. Thesis, Leh igh University; 1992, Ph.D. Thesis, Lehigh University); who investigat ed heat transfer enhancement due to unsteady flow through such an obst ructed channel. Particle advection shows that Bow regimes which are pr edicted to give good mixing based on snapshots of instantaneous stream line contour plots were not necessarily able to efficiently mix fluid which started in the cavity regions throughout the channel. The use of Poincare sections shows regular regions existing under these conditio ns which inhibit efficient fluid transport. These regular regions are found to disappear when the unsteady Bow velocity is increased. (C) 19 97 Elsevier Science Ltd.