Liquid Migration in the Paste as the Result of Consolidation

The processing of various powder materials is often done by an extrusion process; the powders being formed into a paste by the addition of a liquid substance. During extrusion, by reason of the extrusion pressure, some properties of the paste are changing, which affect its rheology and thus the extrusion itself. One of the phenomena is the movement of the liquid phase. This paper is focused on monitoring this phenomenon using model material in a simple test device. Its design simulates the effect of pressure in the extruder. The results of the measurements provide a picture of the movement of the liquid phase under the influence of the pressure in the porous skeleton formed by the powder material.

Monitoring imbibition dynamics at tissue level in Norway spruce using X-ray imaging

The study of moisture migration in Norway Spruce may reduce the discrepancy between measurements and simulations of transfers in buildings and thus be helpful for improving their performance and durability. For this purpose, X-ray imaging was used to study moisture migration in Norway spruce during imbibition at tissue level. Moisture content kinetics in earlywood and latewood, based on X-ray attenuation, was observed and measured through rigorous protocol. The imbibition process was studied in both longitudinal and radial directions. The results showed an easier migration of liquid in latewood than in earlywood in the longitudinal uptake. In the radial direction, the impact of compression wood as a barrier and the role of the anatomical structure in the liquid migration were highlighted by the direct visualization of filled tracheids.

Liquid migration in flowing granular materials

In partially wet granular beds, liquid migrates between particles due to collisions and contacts. This, in turn, influences the flow behaviour of the granular bed. We investigate liquid redistribution in moving monodisperse particles in a rotating drum using Discrete Element Method (DEM) simulations. For weak capillary forces, liquid re-distribution, induced by the continuous flow of particles, leads to concentration of the liquid in the core of the bed, where the flow is quasi-static. High capillary forces reduce the surface flow speed and granular temperature. This decreases liquid bridges rupturing in the flowing layer, allowing the liquid to remain in the outer region of the bed.