Effect of an unsteady external flow on mass transfer to cavities

Mass transfer to the bottom wall of a rectangular cavity in the presence of an external periodic flow is investigated. Flow unsteadiness is generated by placing a circular cylinder at mid height within a channel. The cavity i s located downstream of the cylinder at the lower wall of the channel. Both experimental measurements and numerical simulations are carried out to est ablish the ability of a time-accurate finite element solver to capture the transient flow and mass transfer. The mass-transfer rate at the bottom wall of the cavity is measured using reduction of ferricyanide ions on a platin um line electrode. Cavity aspect ratios (height/width) of 0.5, 1.0 and 1.81 and Reynolds numbers based on channel heights between 100 and 800 are inve stigated. (C) 1998 Elsevier Science Ltd. All rights reserved.