The Accumulator subnode is available from the context menu (right-click the Velocity Reinitialization parent node) or from the Physics toolbar, Attributes menu. Each Accumulator subnode defines a variable, called the accumulated variable, in the domains where the parent Velocity Reinitialization is applied. Whenever a particle is affected by the Velocity Reinitialization, whether its velocity is actually changed or not, the value of the accumulated variable in that element is incremented based on the value of the user-defined Source term R for the particle.

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

Enter the Accumulated variable name. The default is rpv. 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 Velocity Reinitialization node in an instance of the Mathematical Particle Tracing interface using the default variable name rpv, the accumulated variable name might be pt.vre.vacc1.rpv.

Enter a Source R. The unit of the source term depends on the settings in the Units section. Whenever the velocity reinitialization condition for the parent node is satisfied, the accumulated variable is incremented by the source term in the mesh element the particle occupies. If the Accumulator type is set to Density, the source term is divided by the volume of the element (in 3D) or area of the element (in 2D).

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.