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 timeAbout 5 minutes using 8 MPI tasks and 8 cores on an HPC; or about 10 minutes on two laptop cores
Results (227MB)Kerr-Schild_Multipole-20210516.tar.gz

This example was last tested on 16-May-2021.


BH horizons

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 and Kerr-Schild_Multipole.session.gui .

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

  • Start VisIT;
  • 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.