Is that you want to let the gas leave the domain, while prevent the solid particles exit from the PO? If so, you can do it alternatively by adding a keyword: bc_po_apply_to_des(2)= .false.
Is that you want to let the gas leave the domain, while prevent the solid particles exit from the PO? If so, you can do it alternatively by adding a keyword: bc_po_apply_to_des(2)= .false.