Flows Through Real Porous Media: X-Ray Computed Tomography, Experiments, and Numerical Simulations

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Wim-Paul Breugem ◽  
Vincent van Dijk ◽  
René Delfos

Two different direct-forcing immersed boundary methods (IBMs) were applied for the purpose of simulating slow flow through a real porous medium: the volume penalization IBM and the stress IBM. The porous medium was a random close packing of about 9000 glass beads in a round tube. The packing geometry was determined from an X-ray computed tomography (CT) scan in terms of the distribution of the truncated solid volume fraction (either 0 or 1) on a three-dimensional Cartesian grid. The scan resolution corresponded to 19.3 grid cells over the mean bead diameter. A facility was built to experimentally determine the permeability of the packing. Numerical simulations were performed for the same packing based on the CT scan data. For both IBMs the numerically determined permeability based on the Richardson extrapolation was just 10% lower than the experimentally found value. As expected, at finite grid resolution the stress IBM appeared to be the most accurate IBM.

Author(s):  
Wim-Paul Breugem ◽  
Vincent van Dijk ◽  
René Delfos

A computationally efficient Immersed Boundary Method (IBM) based on penalized direct forcing was employed to determine the permeability of a real porous medium. The porous medium was composed of about 9000 glass beads with an average particle diameter of 1.93 mm and a porosity of 0.367. The forcing of the IBM depends on the local solid volume fraction within a computational grid cell. The latter could be obtained from a high-resolution X-ray Computed Tomography (CT) scan of the packing. An experimental facility was built to determine the permeability of the packing experimentally. Numerical simulations were performed for the same packing based on the data from the CT scan. For a scan resolution of 0.1 mm the numerical value for the permeability was nearly 70% larger than the experimental value. An error analysis indicated that the scan resolution of 0.1 mm was too coarse for this packing.


2019 ◽  
Vol 46 (4) ◽  
pp. 248-255 ◽  
Author(s):  
Lucile Deloire ◽  
Idris Diallo ◽  
Romain Cadieu ◽  
Mathieu Auffret ◽  
Zarrin Alavi ◽  
...  

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1230
Author(s):  
Fabien Léonard ◽  
Zhen Zhang ◽  
Holger Krebs ◽  
Giovanni Bruno

The mixture of ammonium nitrate (AN) prills and fuel oil (FO), usually referred to as ANFO, is extensively used in the mining industry as a bulk explosive. One of the major performance predictors of ANFO mixtures is the fuel oil retention, which is itself governed by the complex pore structure of the AN prills. In this study, we present how X-ray computed tomography (XCT), and the associated advanced data processing workflow, can be used to fully characterise the structure and morphology of AN prills. We show that structural parameters such as volume fraction of the different phases and morphological parameters such as specific surface area and shape factor can be reliably extracted from the XCT data, and that there is a good agreement with the measured oil retention values. Importantly, oil retention measurements (qualifying the efficiency of ANFO as explosives) correlate well with the specific surface area determined by XCT. XCT can therefore be employed non-destructively; it can accurately evaluate and characterise porosity in ammonium nitrate prills, and even predict their efficiency.


2021 ◽  
pp. 105-113
Author(s):  
A.A. Demidov ◽  
◽  
O.A. Krupnina ◽  
N.A. Mikhaylova ◽  
E.I. Kosarina ◽  
...  

The question of the quality of samples made of polymer composite materials and its verification by x-ray computed tomography is considered. The capabilities of North Star Imaging X5000 tomograph were studied and the samples from PCM were examined for detection and evaluation of the porosity volume fraction. The factors influencing the accuracy of the estimation of the porosity volume fraction are investigated. Namely the size voxel, a filter material, quantity of projections. On the other hand, the size вокселя defines resolution of the digital image, the relation depends on a material of the applied filter a signal/noise, productivity of control worsens with growth of quantity of projections. The choice of optimum values of the listed parametres is necessary for satisfactory quality received tomographic images.


2020 ◽  
Author(s):  
Elnaz Shahriarinia ◽  
Silvio Jose Gumiere ◽  
Christian Dupuis

<p><strong>Estimating the depth of the restrictive layer of soil in a cranberry field based on CT scan images</strong></p><p> </p><p>Cranberry production is a dominant culture in Québec, Canada. In cranberry production, there is a substantial need for water whether for irrigation, harvesting, or frost control. Some farms are implementing subirrigation procedures in order to reduce water use and increase fruit yields. However, this irrigation method may impose hydraulic stresses on soil particles which results in the movement of fine particles. The accumulation of the soil particles in narrow pore throats leads to the formation of restrictive layers in soil.  In this respect, we are going to study the changes in soil media and its porosity based on X-ray computed tomography (CT) which is a non-destructive imaging method. Consequently, X-ray CT has become a great asset to analyze soil physical properties. With the analysis of the images captured by the use of X-ray computed tomography, it is possible to visualize and analyze the pore network structure in the soil media.</p><p> </p><p>This study reports the results of subirrigation experiments for four different sandy soils. These column experiments aimed to reproduce the effects of subirrigation in cranberry fields for 40 years. Seven different time steps were taken with a medical CT scanner SOMATOM Definition AS+ 128 (Siemens, Germany). The 2-D horizontal 16-bit gray-scale images were captured by an X-ray energy level of 140 KeV. For each column, we got 1677 images of 512  512 pixels with a voxel size of 0.1 × 0.1 × 0.6 mm (x, y, z). Studying our images for further analysis, we used several global and local methods to find the most reliable and efficient one to binarize our images. Results show that the methods and the image analysis neighborhood have a great impact on the accuracy of the image segmentation. We were able to reconstruct a 3-D visualization of the soil pore network for each column. We used this reconstruction to demonstrate that the variation of porosity and soil pore characteristics can be studied over time. We find that the transport of soil particles tends to be highest when there are fine sandy soil particles on top of a layer of coarse soil. These finer particles have sufficient energy to be remobilized within the pore network while coarser particles remain in place. Our results show that soil particle transport can be assessed using time-lapse imagery and thus makes it possible to approximate the depth and amount of time that will be required for these restrictive layers to form in different soil profiles. Finally, it would be possible to find the best structure of soil in construction of a cranberry field in the future.</p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p>


2019 ◽  
Vol 196 ◽  
pp. 104-115 ◽  
Author(s):  
Matthew D.R. Kok ◽  
Rhodri Jervis ◽  
Tom G. Tranter ◽  
Mohammad A. Sadeghi ◽  
Dan J.L. Brett ◽  
...  

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 329
Author(s):  
Shidi Yang ◽  
Qiaoli Xu ◽  
Chengcheng Liu ◽  
Xin Lu ◽  
Xuanhui Qu ◽  
...  

In this study, X-ray computed tomography was used to analyze powder binder separation in TC4 green bodies. Firstly, for the scanned results of the whole green body, because of the relative low resolution (36 µm), the powder binder separation can only be analyzed by using gray value distribution. Then, local regions (areas near the gate and the central parts) were scanned by using a much higher resolution (2.3 µm). Both of the volume fraction of powder content and gray value distributions indicate that powder particles tend to accumulate in the central parts. Finally, based on the results tested by using submicron resolution (0.8 µm), the effects of the volume and morphology of the powder particles on the powder binder separation were analyzed.


2010 ◽  
Vol 163-167 ◽  
pp. 3061-3066 ◽  
Author(s):  
Jian De Han ◽  
Gang Hua Pan ◽  
Wei Sun ◽  
Cai Hui Wang ◽  
Hui Rong

X-ray computed tomography (XCT), a non-destructive test, was used to study three dimensional (3D) meso-defect volume distribution changes of cement paste due to carbonation. The 3D meso-defect volume from 0.02mm3 ~5mm3 before and after carbonation was analyzed through add-on modules of 3D defect analysis. The experimental results show that the meso-defect volume fraction before and after carbonation are 0.7685% and 2.44%, respectively. After carbonation, the smaller defect increased significantly than the bigger defect.


Author(s):  
Guangfa Yao

Abstract Immersed boundary methods have gained increasing attention in modeling fluid-solid body interaction using non-body conforming computational fluid dynamics, due to their robustness and simplicity. They usually do this by adding a body force term in the momentum equation. The magnitude and direction of this body force ensure that the boundary condition on the solid-fluid interface is satisfied without invoking complicated body-conforming numerical methods to impose the boundary condition. The body force is usually calculated and imposed using some interpolation or extrapolation around the solid-fluid interface. It can also be calculated based on the solid volume fraction in the cells around the solid-fluid interface. Therefore, it is critical to have a robust method to represent or track arbitrary solid bodies immersed in a fluid field and facilitate the needed interpolation, extrapolation, or calculation of solid volume fraction. To that end, the level set method has been used as a robust method to represent and track arbitrary solid bodies in a fluid field. In the presented paper, the level set based approaches used to handle arbitrary solid bodies in a fluid field are reviewed, and a new higher order method is presented to resolve the solid-fluid interface using the given level sets at each grid point.


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