### 10.10.9. Parts - Fill - Block Remap

This window lets you write fill data to or from datafiles (.fil) for performing fast block remaps.

The standard remapping scheme for 3D to 3D Euler-FCT is very useful in blast modeling but in certain circumstances can take a very long time to search for the cells in the remapping range, especially if the part size is very large, for example more than 2 million cells.

The "fast block" remapping command maps several cells from a fine mesh of a small space into a single cell in a relatively coarse mesh of a large space, directly without searching for the remapping range. Thus the efficiency of the remapping process has been improved dramatically.

The fast block remapping procedure is applicable to Euler-FCT parts only. The scheme allows unused cells in the remapping region. However, cover fractions are not considered in the remapping calculations so block remapping should not be applied to any region of the part where Euler-FCT/Lagrange or Euler-FCT/Shell coupling takes place.

Write Datafile

  Select this option if you want to write fill data for the current Part to a .fil file.

Read Datafile

  Select this option if you want to read fill data for the current Part from a previously written .fil file.

Filename

  The file name (do not append .fil)

Typical steps that will be undertaken when using Block Remapping for blast problems are as follows:

1. Load the original building data file.

2. Modify the part so it only contains a small area of the explosive and the surrounding buildings.

3. Refine the mesh, then remap 1D or 2D data to the refined part.

4. Save the file and start calculation.

5. At the wrap-up cycle (when the explosive wave approaches the boundary of the refined part), output the blast field to a remap file.

6. Load the original building data file again.

7. Modify the part so it contains a larger area.

8. Refine the mesh.

9. Read the remap file.

10. Save the file and continue running.

11. Repeat 5-10 as necessary.

An example of an analysis of a blast in a city center that was performed using the block remapping facility is shown below. The city center is represented using an Euler-FCT mesh with unused regions to represent buildings as shown below. Note that the original zoning and fill operations for this model were set up using the new block fill command.

To perform the initial expansion of the blast the central section of the grid, as shown below in figure a, is taken and refined by a factor of 4 as shown in figure b.

The analysis of the detonation of the spherical charge is initially performed using a 1D wedge analysis which is then remapped into the refined grid as shown below. The expansion of the blast wave in the central region of the city is then performed using the refined 3D Euler-FCT grid until the wave front reaches the boundaries of the refined region as shown in figure b. At this point the results for this analysis are written to a block remap data file named BLKRP1.

Following the creation of the remap data file BLKRP1 the original model is subsequently reloaded and a larger region of the Euler-FCT part is analyzed as shown below in figure a. This section is refined by a factor of 2 in all directions to give the resulting mesh shown in figure b.

The results stored in file BLKRP1 are then remapped into the refined grid to give the initial conditions for the second phase of the analysis as shown below in figure a. The propagation of the blast wave can then continue until again the wave front approaches the boundaries of the refined region as shown in figure b. At this stage a further block remap data file is written named BLKRP2.

The final stage of the analysis can be performed using the full model. This model is reloaded and the results stored in file BLKRP2 are remapped into the entire Euler-FCT part to give the initial conditions for the final phase of the analysis as shown below in figure a. The propagation of the blast wave can then be tracked though the remainder of the city center as shown in figure b.

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