The Thermal Re-Emission feature diffusely reflects particles from a boundary, like the Wall with the Diffuse scattering wall condition. Unlike the Diffuse scattering condition, however, the Thermal Re-Emission feature also re-samples the particle speed from a distribution based on the temperature of the boundary.

Enter the Temperature T (SI unit: K). If the temperature is computed by another physics interface then it can be selected from the list.

Enter a value or expression for the Freezing probability γ (dimensionless). The default is 0. This is the probability (a number from 0 to 1) that a particle will be absorbed by the wall and not be re-emitted. For 0 all particles are reflected into the modeling domain, while for 1 all particles are absorbed.

To properly apply this boundary condition to walls that are moving with respect to the domain, select the Subtract moving frame velocity from reflected particle velocity check box, which is cleared by default. Then, from the Background velocity list, select From moving frame (the default) or User defined.

The option From moving frame is only effective if a Rotating Frame node has been added to the model. Then, the selected boundaries are assumed to be stationary with respect to the inertial (laboratory) frame, rather than the rotating frame of reference. If a large number of particles hit the boundary at the same location at the same time, the distribution of reflected particles may be visibly skewed to one side of the surface normal, if the angular velocity of the frame is sufficiently high.

If User defined is selected, enter the components of the frame velocity vb directly.