Gallery: Multipatch wave equation

The Llama code is a 3-dimensional multiblock infrastructure for Cactus based on Carpet. It provides different patch systems that cover the simulation domain by a set of overlapping patches. Each of these patches has local cooordinates with a well-defined relation to global Cartesian coordinates. Information between the different patches is communicated via interpolation in the overlap zones.

Here we show an example evolution of a wave equation on a Kerr background using the "Thornburg2004nc" patch-system, consisting of 90 degree by 90 degree wedges centred on each of the +x, -x, +y, -y, +z, -z coordinate axes. This provides a complete covering of a region between rmin and rmax with smooth inner and outer boundaries. The initial data is an l=2, m=2 spherical harmonic in the angular directions, and a Gaussian in the radial direction. An alternative patch system, "Thornburg2004", adds a cubical patch enclosing r < rmin in which standard Carpet box-in-box mesh refinement can be employed. This is used in the GW150914 gravitational wave gallery example.

We ask that if you make use of the Llama code, then please cite Llama, the Einstein Toolkit, the Carpet mesh-refinement driver and Cactus.

Simulation details

Computational details

Parameter FileKerr-Schild_Multipole.par
Submission commandsimfactory/bin/sim create-submit Kerr-Schild_Multipole --parfile arrangements/Llama/LlamaWaveToy/par/Kerr-Schild_Multipole.par
Total memory800 MB
Run timeA little over 1 minute using 56 MPI tasks and 56 cores on Frontera; or about 10 minutes on two laptop cores
Results (gzip 234MB, uncompressed 468MB)Kerr-Schild_Multipole-20231201.tar.gz

This example was last tested on 6-Dec-2023.


Scalar Wave XY

Projection into the xy plane of an l=2, m=2 multipole evolved with the wave equation on a spherical grid made of 6 coordinate patches. Image created using the VisIt file Kerr-Schild_Multipole.session.

    If the file structure is different than expected in the saved *.session files above, the following VisIt directions might help:

  • Start VisIT; on our cluster "singularity run docker://symerio/visit" works if you do not have it installed.
  • Sources > Open file name like u.file.* as database and select manually CarpetHDF5 as file type.
  • Plots > Add Pseudocolor. Load the data is called "LLAMAWAVETOY--u_lp_MP_rp_" .
  • On Pseudocolor > Add Operator Slice.
  • Click Draw. The defaults are not good and note this is a movie and we show the time stamp at 5.04, Cycle 56.
  • Also click the "Swap foreground / background colors" icon on the Drawing window---icon with white upper triangle and black lower triangle.
  • Double click on the Pseudocolor and select the "orangehot" Color Table, and set the minimum to -0.5 and maximum to +0.5.
  • Double click on the Slice and select Normal>Orthogonal Z Axis to get the X-Y slice plot.
  • From the main controls, with "File" etc on the menu, you can run the movie or use the slider bar under Time to select 0056. You should see the same graphic as in this gallery.