For years, researchers around the globe have had a hard time examining objects at a very small scale, say micrometer level. Such research requires the use of very accurate tools: micro-CT scanners that can retrieve structural information down to this level and state-of-the-art software that has the ability to process and analyze small scale images without any compromise. In the following case study, researchers were looking for a way to understand water flow through Belgian sandstone. The obtained insights will be used for the study of extraction of fossil fuels from porous rock formations. Thanks to the joint expertise of inCT, Materialise and TotalSim, this analysis was made effortlessly.

 

 

Synergy Leads to the Greatest Results

Close-up image of the sandstone sampleOver the years, Materialise has acquired extensive knowledge and expertise in the field of micro-CT data handling. In order to be able to provide its customers with the very best solution to their problem, Materialise has built up a vast network of reliable partners, which all rise to very high standards. Recently, one such successful collaboration led to a CFD simulation of micro-CT sandstone data.

The researchers turned to Materialise to help them with their project. Materialise’s Engineering Services department specializes in solving a wide variety of engineering problems, from start to finish. In order to provide an accurate flow analysis of 2D micro-CT slice, courtesy of inCTthe sandstone data, three areas of expertise were combined. First of all, high quality non-destructively obtained slice images of the specimen were captured. InCT (Ghent, Belgium) provided Materialise with exactly this type of data using their broad micro-CT hard expertise. Next, accurate 3D model generation and surface mesh optimization were performed using the Research Edition of the Mimics Innovation Suite. Finally, this model was used as an input to the volume meshing and solving process performed by the CFD consultancy experts of TotalSim (Brackley, UK).

 

Capturing Micro-CT Image of Sandstone Sample

In order to create the most accurate 3D reconstruction of the sandstone data, Materialise turned to inCT, known for its state-of the-art image capturing techniques. Their customized X-ray CT scanners are configured to produce an optimal result for the high-resolution imaging of geological samples. They use a transmission-type X-ray tube, which was configured to produce an X-ray beam with a spot size of only a few micrometers. During the CT scan, more than 1000 projection images were recorded, while the sample, a 7 mm core drilled from Belgian sandstone (Bray), was rotated accurately over 360°. This resulted in a complete 3D volume of over 1500³ voxels, with an isotropic voxel size of 6 μm, ensuring the images’ accuracy.
 

Generating 3D Model and Surface Mesh

Optimized surface mesh in MimicsNext, a team of Materialise’s Engineering Services experts got to work. The 2D scanned slices were imported into Materialise’s scanner image processing software Mimics, which allowed them to make a separate segmentation of rock material and air. Based on this, they constructed a 3D STL model of a portion of the rock effortlessly. The software’s built-in mesh optimization algorithms yielded a high quality, extremely accurate mesh, ready for export to any major FEA or CFD package.


 

Generating Volume Mesh and Solving

CFD simulation shows total pressure loss in tight constrictions, courtesy of TotalSimThe volume mesh and CFD simulations were performed by the consultants of TotalSim, combining STL based meshing and solving procedures in OpenFOAM with Materialise’s design, mesh and geometry optimization software 3-matic. The water flow was simulated using an incompressible fluid definition, with an inlet speed of 0.05mm/s at the top and left face, and free outlets on the opposing faces. The other faces of the block were defined as impassable symmetry planes. The experts at TotalSim were able to visualize the water flow easily. After studying the flow results, they noticed little non-laminar behavior because of the very low speed of the water. The simulation also showed a drastic pressure change in tight constrictions. The pressure gradient dominates the flow, driving the water through the block as directly as possible.
 

- inCT is a spin-off of the Ghent University and originates from the Centre for X-ray Tomography (UGCT). inCT provides services in non-destructive inspection and material characterization by means of X-ray radiography and microtomography. Using state-of-the-art 2D and 3D imaging techniques, inCT offers a solution to a variety of problems in material research, with a focus on retrieving three-dimensional structural information down to the micrometer level.

- TotalSim is an independent limited company established in 2007. The company was started as a natural replacement for the successful Advantage CFD consultancy that operated as part of the Honda Formula 1 team until 2006. They combine open source, commercial and in-house codes to provide a competitive and fl exible approach to analyses of all sizes.

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