I think it is cause the nozzle region (inlet till the circled position) is an internal flow case, while the bottom domain is an external flow. however, since the circled position is an interior, while my outlet is the pressure outlet at the far right, the mass flow becomes only conserved at the inlet and the pressure outlet at the far right. I think I am setting up my problem correctly besides the circled region since I am unsure how to ensure mass flow is conserved between the interior of the nozzle and the exit of the nozzle when I have an additional external flow domain at the bottom. Appreciate any advice given