[rafsanzn]

Hello, I'm very new to CFD, and I was doing a project on star ccm+ about marine engine room ventilation. The design has an engine room and inside there's an enclosure with the engine inside. The inlet and outlet are on the surface of the enclosure.
I'm attaching a hand-drawn sketch alongside this post.
I'm facing meshing issues like "Surface of the region is not closed" or "Surface is not manifold". It would be very helpful if someone can give me some instructions on meshing. Thanks in advance.