The Accumulator subnode is available from the context menu (right-click the Wall node) or from the Physics toolbar, Attributes menu. Each Accumulator subnode defines a variable, called the accumulated variable, on each boundary element in the selection of the parent node. Whenever a grain hits a boundary element, the value of the accumulated variable in that element is incremented based on the value of the user-defined Source term R for the incident grain. The accumulated variable can be influenced by all grains or be restricted to grains corresponding to a specific release feature or a Grain Properties node.

Select an option from the Accumulator type list: Density (default) or Count.

Enter the Accumulated variable name. The default is rpb. The accumulated variable is defined as <scope>.<name>, where <scope> includes the name of the physics interface node, parent boundary condition, and the Accumulator node; and <name> is the accumulated variable name.

For example, if the Accumulator subnode is added to a Wall node in an instance of the Granular Flow interface using the default variable name rpb, the accumulated variable name might be gran.wp.bacc1.rpb.

Enter a Source R. The unit of the source term depends on the settings in the Units section. Whenever a grain comes in contact with a boundary element in the selection of the parent node, the accumulated variable in that element is incremented by the source term. If the Accumulator type is set to Density, the source term is divided by the area of the boundary element (in 3D) or the length of the boundary element (in 2D).

Select an option from the Grain selection list to specify whether the accumulated variable collects information from the grains based on a Release feature (the default) or a Grain properties node.

If Release feature is selected, select an option from the Release feature list. If All (the default) is selected, the accumulated variable collects information about all grains in the selected domains or boundaries, regardless of how they were released. Alternatively, select a grain release feature from the list, and then only the grains released by that release feature are included.

If Grain properties is selected from the Grain selection list, select an option from the Released grain properties list. If All (the default) is selected, the accumulated variable collects information about all grains in the selected domains or boundaries, regardless of their grain properties. Alternatively, select a grain properties feature from the list, and then only the grains associated with the selected Grain Properties node are included.

Select a Dependent variable quantity from the list; the default is Dimensionless [1]. To enter a unit, select None from the list and in the Unit field enter a value, for example, K, m/s, or mol/m^3.

The accumulated variables are computed using discontinuous shape functions. Select the Compute smoothed accumulated variable checkbox to compute a smoothed accumulated variable by computing the average value of the variable within a sphere of a user-defined radius. Then enter a Smoothing radius r (SI unit: m). The default is 0.1 m.