CONSTELATION

Couples STAR-CCM+ and Serpent 2 for helium-3 injection into TREAT and OSTR

Originally created by Cole Leingang in 2021. Modified by Austin Warren in 2022.

Documentation:

This document details the inputs and usage for the CONSTELATION coupling script. In the Documentation folder, there are other files which cover the individual inputs and usage for the Serpent 2 and STAR-CCM+ portions.

An example transient coupling script can be found at the Serpent 2 wiki: MSCS for coupled transients.

Requirements:

• Python 3 (originally written in 2.7)
• Serpent 2 (version number here)
• STAR-CCM+ (version number here)

Usage:

The CONSTELATION Python script couples STAR-CCM+ and Serpent 2 by managing the interfacing files and re-formatting data. This document will not discuss the creation of the Serpent 2 and STAR-CCM+ models. More discussion on how to use STAR-CCM+ and Serpent 2 models can be found in Documentation/STAR-model.md and Documentation/Serpent-model.md, respectively. Below is a flow chart showing the algorithm of CONSTELATION.

To use CONSTELATION, you will need to have the Serpent 2 and STAR-CCM+ simulations ready to run with the correct file names and paths provided to the CONSTELATION script. Separate documentation is provided for setting up the simulations, found in the Documentation/ folder. Run the script with Python on the computer or cluster of your choice and it will begin the simulations.

user@cluster:~$ python CONSTELATION_3.py

CONSTELATION will queue the jobs on the cluster by submitting job scripts. These job scripts will need to be compatible with whatever server or cluster is being used to run this simulation. Examples are included in this package for use on Idaho National Laboratory's (INL) Sawtooth cluster.

File Structure

Below is an example of the required file structure to use CONSTELATION.

Modifications:

To use this script with a different Serpent 2 input file, simply change the file in the file_in variable, as seen below. The adjusted Serpent 2 input file name can be changed using the file_out variable in a similar manner.

file_in = open(r'Treat',r)

file_in = open(r'ostr',r)

Other file names you may want to change include:

• .ifc files
• Extracted data .csv files
• Serpent detetector files (if you changed the input file name from 'coupledTreat')

CONSTELATION was originally written to couple two separate STAR-CCM+ simulations. If you wish to couple a different number of simulations, then the script must be modified. The ostr_CONSTELATION_3.py file provides an example with only one STAR-CCM+ simulation.

Due to the way CONSTELATION is written, the two parts of the simulation need to finish their respective time steps close together in time. Specifically, the user wants the STAR-CCM+ simulation(s) to be waiting for the Serpent 2 simulation to finish (This is because the SerpentDone.txt file is deleted after 1 minute). It may take some trial and error to determine the best allocation of resources for the users needs.