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Research Papers

On the Characterization of Lifting Forces During the Rapid Compaction of Deformable Porous Media

[+] Author and Article Information
Banafsheh Barabadi

Department of Mechanical Engineering and Cellular Biomechanics and Sports Science Laboratory, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085

Rungun Nathan

Cellular Biomechanics and Sports Science Laboratory, 800 Lancaster Avenue, Villanova, PA 19085; Division of Engineering, Penn State Berks, Reading, PA 19610

Kei-peng Jen

Department of Mechanical Engineering, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085

Qianhong Wu1

Department of Mechanical Engineering and Cellular Biomechanics and Sports Science Laboratory, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085qianhong.wu@villanova.edu

1

Corresponding author.

J. Heat Transfer 131(10), 101006 (Jul 29, 2009) (12 pages) doi:10.1115/1.3167543 History: Received September 30, 2008; Revised April 23, 2009; Published July 29, 2009

In a recent paper, Wu (2005, “Dynamic Compression of Highly Compressible Porous Media With Application to Snow Compaction,” J. Fluid Mech., 542, pp. 281–304) 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 the approach of Wu to various porous materials such as synthetic fibers. The previous experimental setup was completely redesigned, 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 was modified by introducing the damping effect from the solid phase of the porous materials. One uses Carman–Kozeny’s relationship to describe the change in 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 porous materials, 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 inside porous media and is an extension of the previous studies done by Wu

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Schematic of the test setup for finite domain and (b) picture of the actual test setup

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Figure 4

Force/displacement relation obtained in the quasistatic compression experiment with fiber B3

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Figure 5

Representative dynamic pressure response for (a) material B3 with 7.0 kg load and (b) material sample A2 with 9.25 kg

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Figure 6

Representative radial pressure measured by the pressure transducers 1–4 as shown in Fig. 1. The testing material is A2 and the loading on the piston is 9.25 kg. It is plotted at the time when peak pressure is achieved at these locations. The data have been normalized by the maximum pressure obtained by pressure transducer 1 at the center of the piston, Pmax. The error bars in the graph indicate the range of the variation in the pressure measurements in multiple sets of experiments.

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Figure 7

Representative time-dependent displacement of the piston during the dynamic compaction experiment mentioned in Fig. 5 for (a) material B3 and (b) material A2

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Figure 8

Comparison between the acceleration obtained from the direct measurement using accelerometer and the time derivative of the piston displacement described in Fig. 7 for (a) material B3 and (b) material A2

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Figure 9

Comparison between experimental results (solid line) and theoretical simulation (dash line) for the dynamic compaction experiments with material B3 at 7.0 kg loading: (a) displacement of the piston and (b) pore pressure at the center of the piston. The simulation was based on no solid damping effects during compression.

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Figure 10

Comparison between experimental results and theoretical simulation for the dynamic compaction experiments with material B3 at 7.0 kg loading: (a) displacement of the piston and (b) pore pressure at the center of the piston. Two simulations are provided, one for constant permeability at Kp=6.25×10−9 m2 and the other for varying permeability following Eq. 11 with initial value of permeability Kp0=8.79×10−9 m2. In both cases, the solid damping coefficients in compression and expansion are determined as ηd=4.73 s/m and ηu=300 s/m, respectively.

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Figure 11

Comparison between experimental results and theoretical simulation for the dynamic compaction experiments with material B3 at 8.71 kg loading: (a) displacement of the piston and (b) pore pressure at the center of the piston. The initial value of Darcy permeability Kp0=8.79×10−9 m2, and the solid damping coefficients in compression and expansion are ηd=3.33 s/m and ηu=300 s/m, respectively.

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Figure 12

Time-dependent forces during dynamic compression of fiber B3 under 7.0 kg loading

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Figure 2

SEM images for (a) material A at 1kV and 2000× and (b) material B at 1kV and 1800×

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Figure 3

Stereomicroscopy images for material A at bottom layer (a), middle layer (b), and top layer (c), and for material B at bottom layer (d), top layers (e), and top layer in a different region at a higher magnification (f)

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