MPM Restart
This tutorial is intended on showing how to restart a MPM simulation. The Example is based on the Granular Flow Validation test. A picture of this test can be seen below.
Before even launching the simulation it is important to activate the restart capability so that Kratos is saving the restart files in the desired intervals. To do this open the "Results"-tab where the "Restart-Output"-option is found. Here the restart output can be enabled (it is enabled by default) and the output frequency can be defined. The output frequency can be set based on the number of time steps or the time between outputs.
After generating the calculation files the following entries can be found in the "ProjectParameters.json"-file containing the information about the restart process.
At this point, the simulation can be launched normally and Kratos will write the restart files into a folder called "MPM__Material|_restart_files". The restart files will be named "MPM_Material{time step/time}.rest". These files can then be used to restart the simulation if necessary.
Once a simulation has been launched and the restart files have been written, the simulation can be restarted from any of the existing restart files. To do this open the "ProjectParameters.json" and modify the "model_import_settings". The only value that needs to be modified is the "restart_load_file_label" entry. This entry should contain the label of the restart file to be used, i.e. the time step or the time that is given in the "MPM_Material_{time step/time}.rest" name to be used. It is important to write this number as a string!
When launching the simulation again, the simulation will start from the restart file, instead of starting from the beginning. It is important to note, that the previous result outputs (including the restart files) after the point of the restart will be overwritten! So if any specific outputs after the restart time should be saved, they need to be moved to a different folder or renamed.