Rungun Nathan

A biphasic approach for the study of lift generation in soft porous media

Lift generation in highly compressible porous media under rapid compression continues to be an important topic in porous media flow. Although significant progress has been made, how to model different lifting forces during the compression process remains unclear. This is mainly because the input parameters of the existing theoretical studies, including the Darcy permeability of the porous media and the viscous damping coefficient of its solid phase, were manually adjusted so as to match the experimental data. In the current paper, we report a biphasic approach to experimentally and theoretically treat this limitation. Synthetic fibrous porous materials, whose permeability were precisely measured, were subsequently exposed to sudden impacts using a porous-walled cylinder-piston apparatus. The obtained time-dependent compression of the porous media, along with the permeability data, was applied in two different theoretical models to predict the pore pressure generation, a plug flow model and a consolidation...

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 ...

Lift Generation in Soft Porous Media Under Rapid Compaction

In a recent paper, Wu et al. (Journal of Fluid Mechanics 542, 281 (2005)) have developed a novel experimental and theoretical approach to investigate the dynamic lift forces generated in the rapid compression of highly compressible porous media, (e.g. snow layer), where a porous cylinder-piston apparatus was used to measure the pore air pressure generation and a consolidation theory was developed to capture the pore pressure relaxation process. In the current study, we extend Wu et al.’s approach to various porous materials such as synthetic fibers. A complete redesign of the previous experimental setup was done, where an accelerometer and a displacement sensor were employed to capture the motion of the piston. The pore pressure relaxation during the rapid compaction of the porous material was measured. The consolidation theory developed by Wu et al. was modified by introducing the damping effect from the solid phase of the materials. One uses Carman-Kozeny’s relationship to describe the change of the permeability as a function of compression. By comparing the theoretical results with the experimental data, we evaluated the damping effect of the soft fibers as well as that of the pore air pressure for two different synthetic fibers, A and B. The experimental and theoretical approach presented herein has provided an important methodology in quantifying the contributions of different forces in the lift generation in soft porous media and is an extension of the previous studies done by Wu and others.Copyright