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. 2022 Jan 30;8(2):32.
doi: 10.3390/jimaging8020032.

Visualization of Interstitial Pore Fluid Flow

Linzhu Li  1 , Magued Iskander  1
Affiliations

Visualization of Interstitial Pore Fluid Flow

Linzhu Li et al. J Imaging. .

Abstract

Pore scale analysis of flow through porous media is of interest because it is essential for understanding internal erosion and piping, among other applications. Past studies have mainly focused on exploring macroscopic flow to infer microscopic phenomena. An innovative method is introduced in this study which permits visualization of interstitial fluid flow through the pores of a saturated synthetic transparent granular medium at the microscale. Several representative images of Ottawa sand were obtained using dynamic image analysis (DIA), for comparison with flow through perfect cylinders. Magnified transparent soil particles made of hydrogel were cast in 3D printed molds. Custom 3D printed jigs were employed for accurate positioning of the particles to ensure that particles have the same flow area within the soil. The pore fluid was embedded with silver-coated hollow microspheres that allowed for their florescence and tracking their movement within the model when illuminated by a laser light source. Images of the flow were captured from the model using a high-speed camera. This, along with particle image velocimetry (PIV) provided for the velocity and direction analysis of fluid flow movements within the pore space of a planar 2D model. Comparison of interstitial flow through homogeneous porosity-controlled Ottawa-shaped and cylindrical particles demonstrates that the magnitude of turbulence is related to particle roundness.

Keywords: granulometry; inter-particle; microscale; roundness; shape.

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Conflict of interest statement

The authors declare no conflict of interest and certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.

Figures

Figure 1
Figure 1
Test setup used to visualize fluid flow through pores of a granular material.
Figure 2
Figure 2
Graphical explanation of particle size and shape descriptors.
Figure 3
Figure 3
Images of Ottawa #20-30 sand particles captured using Dynamic Image Analysis (Top) compared to synthetic circular particle (bottom).
Figure 4
Figure 4
3D printed molds for casting enlarged extruded Ottawa #20-30 particles. Note Hydrogel modelled particles cast in the molds.
Figure 5
Figure 5
Testing apparatus showing hydrogel particles placed at a fixed porosity and saturating water infused with fluorescent nano particles.
Figure 6
Figure 6
Custom template employed for precise distribution of particles within the model. (a) 3D printed template (top), and (b) template with hydrogel particles placed within it (bottom).
Figure 7
Figure 7
CAD models of custom 3D printed filters employed for distribution of flow within the model (corresponding to filters shown in Figure 5).
Figure 8
Figure 8
Overall procedures for visualization of interstitial pore fluid flow.
Figure 9
Figure 9
Typical flow images captured by the high-speed camera for (a) cylindrical particles and (b) simulated Ottawa sand. Note triangular zones used for analysis of flow superimposed over the captured images.
Figure 10
Figure 10
Flow images analyzed using Particle Image velocimetry (PIV) for (a) cylindrical particles and (b) simulated Ottawa sand.
Figure 11
Figure 11
Comparison of mean interstitial flow velocities in 8 consecutive frames for flow between (a) Cylinders (top) and (b) simulated Ottawa sand particles (bottom).
Figure 11
Figure 11
Comparison of mean interstitial flow velocities in 8 consecutive frames for flow between (a) Cylinders (top) and (b) simulated Ottawa sand particles (bottom).
Figure 12
Figure 12
Comparison of average (a) discharge and (b) seepage velocities between perfect cylinders and simulated Ottawa sand particles.
Figure 13
Figure 13
Distribution of flow velocities in between (a) Cylindrical particles (T = 2 s) and (b) simulated Ottawa sand particles (T = 0.248 s).
Figure 13
Figure 13
Distribution of flow velocities in between (a) Cylindrical particles (T = 2 s) and (b) simulated Ottawa sand particles (T = 0.248 s).
Figure 14
Figure 14
Comparison of hydraulic conductivities (velocity v, normalized by hydraulic gradient, i) between Cylindrical particles and simulated Ottawa sand particles. (a) Discharge velocity, and (b) Seepage velocity.
Figure 15
Figure 15
Comparison of the orientation of flow trajectories between (a) cylindrical particles and (b) simulated Ottawa sand particles.
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