Oscillatory flow: Effect on transverse diffusivity and inertial migration of particles and bubbles

Oscillatory flow has numerous interesting and useful applications, many of which take advantage of oscillatory flow's unique features. Two processes which benefit from oscillatory flow are investigated herein: the first, using oscillatory flow to enhance mass transport in a porous medium, and the second, developing separation strategies from the study of inertial migration of particles and bubbles in oscillatory flow.;The effect of oscillatory flow on mass transport in a porous medium was studied both fundamentally, in a model porous medium, and specifically, in the direct methanol fuel cell (DMFC). In the limit where the oscillatory flow could be considered quasi-steady, it was found that the transverse diffusivity of a solute could be predicted accurately using a steady flow model. The transverse diffusivity was observed to increase a factor of 104 over the molecular diffusivity. Enhancement in the transverse diffusivity was observed in the DMFC, where the mass transfer resistance of the system was reduced by superimposing fluid oscillations on the anode feed. The oscillations increased the peak power density by up to 30% and the limiting current density more than twofold. An optimization study was performed which examined the effect of other variables relative to the mass transfer resistance of the DMFC. A promising alternative use of oscillatory flow in the DMFC was discovered during this study: it assists with carbon dioxide bubble management at low steady feed rates.;Inertial migration of particles and bubbles in oscillatory tube flow was investigated in both the horizontal and vertical orientations. In the horizontal case, particle mobility was controlled by the ratio of the inertial force to the gravitational force and can be predicted using existing steady flow theories. This result suggested a particle/bubble removal technique using an asymmetric oscillatory flow. An asymmetric oscillatory flow was used to remove bubbles in the DMFC and stabilize its performance. In the vertical case, oscillatory flow was used to stabilize or reverse the net drift of non-neutrally buoyant particles. A simple asymptotic model was developed which is consistent with the experimental data and suggests a possible particle separation strategy.