If Specify mass flow rate is selected from the Particle release specification list in the physics interface Particle Release and Propagation section, the Boundary Load subnode is available from the context menu (right-click the Wall parent node) or from the Physics toolbar, Attributes menu. The Boundary Load subnode uses accumulated variables on each boundary element in the selection of the parent node to calculate the force due to the impact of particles.

Select a Type: Pressure (the default) or Force per unit area. For Force per unit area accumulated variables are defined for components of the boundary load vector. For Pressure one accumulated variable is defined for the normal force per unit area in each boundary element.

The accumulated variable is piecewise discontinuous across different boundary elements. Select the Compute smoothed accumulated variable checkbox to define a spatially smoothed accumulated variable; at each point on the boundary, the smoothed accumulated variable is the average of the accumulated variable over a circle. Enter a Smoothing radius r (SI unit: m). The default is 0.1 m.