Volume Junction Scalar Variables

Background

Several components inherit from VolumeJunctionBase:

Here, these components will be referred to as "junctions". Before, these components all created scalar solution variables for various quantities. However, it was found that this was extremely costly due to the sparsity pattern requirements, thus making simulations involving large numbers of these components to be very slow to initialize. A new option, "use_scalar_variables", has been added to these components, with a default value of true, resulting in the old behavior. The new behavior, enabled by setting this parameter to false, is to create field variables instead of scalar variables, with a single node and node-element added to the mesh for each of these components added to the simulation, and a single degree of freedom per variable. Mathematically, the old and new implementations are equivalent. Additionally, it was found that having large numbers of unique variable names was also detrimental to performance, so this change also changes the naming of junction variables: before, junction variables were named to include the name of the component, e.g., junction1:rhoV. Now, since these variables are tied to the mesh, they can have a common name, e.g., rhoV.

schooltip:Visualizing junction solutions

Since these variables are now located on the mesh, they can visualized alongside the other field variables, such as from pipes. In Paraview, the junction can be made more visible using the "point size" parameter.

Instructions

The old behavior is now deprecated and will be removed in the near future. To switch to the new behavior, set "use_scalar_variables" to false and note the following additional changes that may be necessary:

  • If references to junction variable names were made in the input file, these will need to be updated to remove the component name. For example, the variable name component1:rhoV should become rhoV.

  • If you have regression tests and see Exodiff failures, it is because the mesh is now different, since it has additional mesh nodes and elements for the junctions, so "gold" files will need to be updated.