Match SVF Distribution
The Match Solid Volume Fraction (SVF) Distribution command allows to re-distribute the GAD objects of the current structure such that a desired inhomogeneous solid volume fraction distribution is reached. A specialized form of this algorithm is also available in FiberGeo and GrainGeo, where a Gaussian random field is created and used directly in the generation step to achieve an inhomogeneous distribution. Here, the algorithm can be used in a more general way.
Required input is a generated structure with GAD object information and periodic domain, and an arbitrary solid volume fraction distribution, defined through a GeoDict Volume Fraction (.gvf) input file. Such a file is created in FiberGeo or GrainGeo when the Match Solid Volume Fraction (SVF) Distribution was chosen. It can also be created using the Create Gaussian Random Field command available from the context menu of the Volume Files project status section entry (this feature is only available if FiberGeo or GrainGeo is licensed).
Alternatively, use 3D Inhomogeneity in MatDict to create a distribution based on a CT-scan or a mask structure (see example) or use the GeoPython library or other tools to create a file with the desired input values yourself.
Clicking the Options’ Edit… button opens the Match SVF Distribution dialog where additional parameters can be entered.
Result File Name
As usual, the name entered here is used for the created .gdr file and the corresponding folder.
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Solid Volume Fraction File
Click Browse… to search for the .gvf file here. The chosen file must match to the current structure in the sense that the domain size (in physical length, not in the number of voxels) must be the same.
The absolute SVF values in the file are not important, as the distribution in the file is scaled to match the mean solid volume fraction of the loaded structure. The solid volume fraction file should have a coarser resolution as the structure file, otherwise the computation time will become large. For many cases a 10 times coarser resolution works well, meaning it has a voxel length of 10 µm when the original structure has a voxel length 1 µm.
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Random Seed
The algorithm tries to achieve the given SVF distribution by modifying the GAD objects. This is done in a random order and the given random seed determines the order. Thus, different random seeds will lead to different results.
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Allow Shifts
If checked, objects may be shifted to achieve the desired SVF distribution.
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Allow Deformations
If checked, the objects will be deformed to achieve the desired SVF distribution. This applies only to objects that can be deformed at all. For example, fibers can be deformed, but not spherical grains.
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Periodic Force in Z-Direction
If checked, the force is periodic in all three directions, which is recommended for most cases.
If unchecked, the force is periodic in X- and Y-direction, but not in Z-direction. In that case, the objects are repelled from the domain boundary in Z-direction. This requires that some empty space is available at the top and bottom of the structure.
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Write Object Trajectories
Stores the object movement in a GeoDict trajectory file (*.gpt), which can be visualized in GeoDict.
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Write Intermediate Results
Stores intermediate results, e.g., for the structure after each iteration.
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Error Bound (Stopping Criterion)
In each step, the objects are shifted and deformed and the difference to the desired solid volume fraction is computed. Afterwards, the new difference is used to do the next iteration. This enables to compute how much the solid volume fraction (SVF) has changed in the last iteration and to define a tolerance value for which the simulation should be stopped. This is the recommended stopping criterion.
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Number of Iterations (Stopping Criterion)
The process can also be stopped after a certain number of iterations has been done.
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