SOLIDWORKS Design & Help

Hi, i need help for my engineering design project on starccm, I simplified the valve geometry but i can not assign regions for internal flow. My lecturer suggested that i should use subtract. So i subtrect housing and ball valve. Target body was housing. I tried everything, i tried to extrect internal volume from cad. It kinda worked but had problem with mesh. I really need help. I wouldnt write here otherwise. Is there anyone to help me?