Hydraulic properties of thin fibrous layers

What is it about?

We presented our results of a series of experiments for obtaining the capillary pressure-saturation relationship of a thin hydrophilic non woven fibrous layer. The effects of overburden pressure imposed on a layer, the use of consecutive imbibition-drainage cycles, and increasing the number of layers were investigated for two different materials: a thermally bonded non-woven polyolefin layer with bonding points and a chemically bonded polyester layer without bonding points.

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Why is it important?

The overburden pressure imposed on a single thin layer had a significant effect on the measured capillary pressure-saturation curves. This is because ofcompressibility of the non woven fibrous layers. As a result of applying overburden pressure, the porosity and permeability also changed notably. These two parameters were employed for scaling the capillary pressure-saturation curves based on Leveret’s J function. Experimental results could be matched satisfactorily with this scaling approach. Increasing the number of layers had only minor effects on the measured capillary pressure-saturation curves. However, the dynamic process was totally different for a single layer compared to two layers. The effect of consecutive imbibition-drainage cycles was also reported in the second chapter. The main imbibition curves moved toward higher saturations and higher capillarities compared to primary imbibition because the polyolefin layer contained some fluid at the beginning of main imbibition and had higher surface energy. We also improved the experimental setup to reduce the artefacts in the measurement of a single thin fibrous layer due to the small volumes involved in such experiments.