| For a monolith to be useful in catalytic reactions, a high surface area coating must be deposited upon its surface. Chapter B presents a general framework for understanding the coating of monolithic structures for which the catalyst support material is deposited on the walls of a large number of millimeter-sized square channels. The coating is typically done in two steps; filling the channels with the liquid to be coated followed by blowing the excess liquid out with air. Each of these steps contribute to a fraction of the total coating load. The goal of this work was to understand the coating process in terms of the flow mechanisms in the individual channels of the monolith.; General purpose techniques for visualizing small-scale flows have been developed. These techniques are capable of determining: (i) detailed two-dimensional flow fields; (ii) position, shape, and velocity of fluid-fluid interfaces--including dynamic and static wetting lines and apparent contact angles; (iii) automatic determination of velocity fields along linear streamlines. These techniques are used in Chapters C, D, E, and G to study the movement of solid/liquid/fluid contact lines, the motion of bubbles in square tubes, and the flow and stability of annular films, respectively.; The detailed theoretical analysis of the motion of bubbles and subsequent stability of the annular films in square tubes relies on an analytical expression for the velocity profile in the film flowing between the bubble and the square tube walls. This velocity profile is developed as an infinite series solution in Chapter E. The solution is compared with results obtained from the finite element method and experiment. In Chapter F, the problem of a long inviscid bubble displacing a viscous liquid in square tube is analyzed. The analysis reveals the dependence of the deposited annular film on the dimensions of the square channels, the velocity of the invading bubble, and the properties of the fluid: viscosity, surface tension, and density. The solution is compared with experimental results and the limits of the theory are examined. |
