Permeability measurements for random soft porous medium and its implications to lift generation

In the past decade, foundations have been laid for understanding the lift generation in a soft porous medium under rapid compaction (Feng and Weinbaum [1], Wu, et al. [2,3], Barabadi, et al.[4], Al-Chidiac, et al. [5]). One of the key parameters that affect lift generation is the variation of the Darcy permeability as a function of its compression. This critical component is experimentally investigated in the current study using a permeameter. Two soft, synthetic, porous materials were chosen for the study. The microstructures of these materials were characterized using a Scanning Electronic Microscope. By carefully controlling the air flows through the materials contained in a long Plexiglas tube, consistent results were obtained for their permeability as a function of porosity. One observed a highly non-linear relationship between the permeability and the porosity for both materials. A noticeable difference in the permeability in the high porosity range was observed when the microstructure was altered from fluffing the material. The results were then compared against established expressions for permeability as a function of porosity. It was shown that the Nogai relationship [6] provided the best fit for the permeability of the fibrous material in this study.