The diffusivity of substances, such as moisture, through polymer composites is often described by an effective macroscopic quantity, even though microscopically the might be far from uniform. In this work, we study theoretical example a permeable matrix containing equal-sized impermeable spheres. We assume that, due to interface effects, in vicinity spheres higher than its bulk diffusivity. Usi...

Finger millet (Eluesine coracana) and foxtail millet (Setaria italica), are highly nutritious minor millets and hence is used in most of the staple foods. The present study was to estimate the thin layer drying characteristics of foxtail and finger millet and developing a thin layer model which adequately fits the data. Foxtail and finger millet with an initial moisture content of 0.314 and 0.3...

The produced liquid water in the cathode catalyst layer (CCL) has a signi cant effect on the operation of a proton exchange membrane fuel cell (PEMFC). To investigate this effect, the transport of oxygen in the CCL in the presence of immiscible liquid water is studied by applying a two-dimensional pore scale model. The CCL was reconstructed as an agglomerated system. To explore the wettability...

We present a theoretical and numerical study of wave-induced particle dispersion due to random waves in the rotating shallow-water system, as part of an ongoing study of particle dispersion in the ocean. Specifically, the effective particle diffusivities in the sense of Taylor (Proc. Lond. Math. Soc., vol. 20, 1921, p. 196) are computed for a small-amplitude wave field modelled as a stationary ...

By means of rather general arguments, based on an approach due to Derrida that makes use of samples of finite size, we analyse the effective diffusivity and drift tensors in certain types of random medium in which the motion of the particles is controlled by molecular diffusion and a local flow field with known statistical properties. The power of the Derrida method is that it uses the equilibr...

Silica aerogels prepared by the sol-gel process are often used as solid desiccants in enthalpy wheels for dehumidifying ventilation air in air-conditioning systems. These hygroscopic materials have good moisture adsorption and desorption characteristics due to their porous structure. The current study is focused on the evaluation of the mass diffusivity of solid silica aerogels and silica aerog...

A finite-amplitude propagating wave induces a drift in fluids. Understanding how drifts produced by many waves disperse pollutants has broad implications for geophysics and engineering. Previously, the effective diffusivity was calculated for a random set of small-amplitude surface and internal waves. Now, this is extended by Bühler & Holmes-Cerfon (J. Fluid Mech., 2009, this issue, vol. 638, p...