Boundary Conditions within the UDS while Using Selected and Unselected Zone

Please describe the boundary conditions within the UDS while using the selected and unselected zone?

User defined scalar allows to define any of the advection-diffusion equations. The boundary conditions of UDS can specify the inflow and outflow boundary of the walls. However, you cannot specify the boundary conditions in the boundary surfaces. This can be solved by selecting the zone.

For more details, please refer to the document below: