The Gibbs-Johnson variational approach was applied to thermodynamic treatment of a charged liquid drop placed on a charged substrate. The line tension effect and the presence of charges on the three-phase contact line were taken into consideration. As a result a novel form of the generalized Young equation, containing an electric driving force at the three-phase contact line, was obtained. Application of this relationship to analysis of the electrowetting phenomenon enables us to conclude that the potentialinduced change in the contact angle is the secondary electrocapillary effect, caused by redistribution of the charges on the three-phase contact line.

The impact of non-Newtonian behavior and the dynamic contact angle on the rise dynamics of a power law liquid in a vertical capillary is studied theoretically and experimentally for quasi-steady-state flow. An analytical solution for the time evolution of the meniscus height is obtained in terms of a Gaussian hypergeometric function, which in the case of a Newtonian liquid reduces to the Lucas-Washburn equation modified by the dynamic contact angle correction. The validity of the solution is checked against experimental data on the rise dynamics of a shear-thinning cmc solution in a glass microcapillary, and excellent agreement is found.

Dynamics of spatiotemporal thermal patterns during the catalytic CO oxidation over Pd supported on a glass-fiber catalytic cloth rolled into a tube of 20 mm diameter and 80 mm length has been studied in a continuous flow reactor by IR thermography. A specially designed aluminum mirror built in the reactor provided image of the entire surface of the horizontally held catalytic tube. With flow in the main axial direction and through the tube surface, we observed periodic motions of a pulse, which was born downstream and propagated upstream. The temperature pulse motion was accompanied by conversion oscillations of CO2. With flow in the main axial direction, parallel to the surface, we observed a stationary hot zone after an oscillatory transient. These patterns can be simulated with a plug-flow-reactor-like heterogeneous reactor model that incorporates previously determined kinetic and transport parameters.

Infrared (IR) thermography studies of oscillatory behavior during catalytic oxidation of CO

A mathematical model is formulated to account for experimental infrared thermography observations of spatiotemporal patterns during catalytic oxidation of CO over Pd supported on a glass-fiber disk-shaped cloth in a continuous reactor with feed flowing perpendicular to and through the disk. The model predicts the following observed features: (a) The sustained pattern that the system exhibits is a breathing motion in which a hot spot expands and contracts continuously. This motion emerges due to the imposed cold-edge boundary condition and a qualitative analysis of the experiments supports this suggestion and rules out other mechanisms. (b) The emerging temporally complex patterns can be classified as mixed-mode oscillations with a large relaxation-type conversion peak superimposed with several smaller peaks. (c) The mathematical mechanism that accounts for the change in the number of smaller peaks with varying operating conditions (the reactor temperature) could be characterized as period adding. The mathematical model is based on a published oscillatory kinetics model, and is coupled here with an enthalpy and gas-phase balances with two adjusted parameters. Numerical simulations map the simple and the complex oscillations domains and characterizes the transition between them as either period doubling or period adding.