Enter the Bin Size in units of voxels. The equivalent in metric length units is shown on the right. The bin size determines the range of diameters that belong to one class of solid sizes.

All bins have equal bin size. Beginning with the largest possible diameter that is divisible by the bin size, the diameter is reduced by the bin size in each step. Every voxel is then assigned the diameter of the largest possible sphere that can be fitted in the solid and contains this voxel. Thus, each bin contains solid voxels with an assigned diameter in the range comprised between and , where is the bin number.

For example, when analyzing a porous structure with a voxel size of 1 µm, you can set the bin size to 2 or to 4 (voxels) which would come to classify the solid by their diameter in ranges of 2 µm or 4 µm, and would result in the following bins:

When choosing the bin size, be aware that the underlying algorithm to compute the Euclidean distance operates directly on the voxel grid. Thus, the smallest possible distance between two grid points is 1 voxel, which corresponds to a radius of 1 voxel. This means the smallest diameter that the algorithm will find is 2 voxels. In general, the error made when computing the solid size distribution is of the same order of magnitude as the discretization error of the structure, i.e., 1 voxel.

In the result viewer, for each bin the Minimal Diameter, which is the diameter of the smaller sphere, and the Maximal Diameter, which is the diameter of the larger sphere, are given. This means all solid voxels in that bin have a diameter that is larger than the minimal diameter and smaller or equal than the maximal diameter.

Control how many threads are used for the computation. Parallelization is possible if your license and hardware allow it.

The Parallelization Options dialog opens when clicking the Edit button and you can choose between Sequential, Parallel (Shared Memory), or Automatic Maximum of Threads.

Selecting Sequential will not apply parallelization and only one thread is used for the computation.

When Parallel (Shared Memory) is selected, the Number of Threads can be entered. Below, the Number of CPU Cores that the current machine has, the maximum number of Licensed Threads and the number of those licensed threads that are available (Available Threads) are shown in the dialog. Of course, the maximal number of parallel processes you can use, is the smallest of those three numbers.

If Automatic Maximum of Threads is selected, the number of parallel processes is automatically selected for optimal speed, based on the CPU cores and licensed parallel processes.

The Automatic Local Maximum of processes is automatically selected, which is the minimum of Number of CPU Cores, Licensed Threads, and Available Threads.

The Domain Boundary Conditions can be chosen to be Symmetric, Periodic, Encase, or any combinations of those boundary conditions in all three directions with the choice of Expert.

Choosing the appropriate boundary condition depends on the structure’s design.

For example, imagine a structure with a cross-section as shown below.

For the three boundary condition options the resulting solid size is visualized in blue.

• If Symmetric boundary conditions are taken, the geometry is mirrored at the domain boundary.

• If instead the expected pattern of the geometry is repeated in all directions, Periodic boundary conditions should be selected. That has the effect that the objects and pores of the structure that end on one side of the structure reappear on the opposite side.

• If the structure should be encased with a closed wall, the Encase boundary conditions are used.

Check Expert to apply different boundary conditions for each direction. You can combine the three above mentioned boundary conditions independently for the directions. For example, the boundary conditions could be chosen to be Encase in X-direction, Symmetric in the Y-direction and Periodic in Z-direction.

When Write Pore Geometries as *.gdt Files is checked, files in *.gdt format are saved in the automatically created results folder inside the project folder. The amount of these *.gdt files reflects the number of pore size steps and depends on the entered Bin Size. A large bin size results in fewer size steps, and thus, fewer *.gdt files are saved for the visualization. For each bin, a separate *.gdt file is written, where every voxel of the pore space is assigned to one of the specified materials.

In the *.gdt file of a certain bin, a voxel is assigned to the first material if it belongs to a lower bin number, i.e., the corresponding pore diameter is smaller. Consequently, all voxels from a bin with the same or higher number are assigned to the second material. This results in two different Material IDs for the voxels in the pore space. The materials written into these *.gdt files can be specified after checking Write Pore Geometries as *.gdt Files. For example, predefined materials of the Material Database, such as Air or Water can be chosen by clicking on the buttons. The current Material IDs for the fluids in the pores are shown at the bottom.

You can load these structure files into GeoDict from the Pore Size Visualization tab in the Result Viewer.

Additionally, when Write Pore Size Distribution as *.gsd File is checked, a file with the default name PoreSizeDistribution.gsd, in *.gsd (GeoDict Size Distribution) format, is saved in the results folder inside the project folder. The file contains the pore size (diameter of sphere) of each voxel written into a volume field that can be loaded from the Pore Size Visualization tab of the Result Viewer.