[vinvalt]

I want to obtain my fluid domain by either extracting the internal volume or using the boolean operation substract or intercepts on my geometry which I imported under; import CAD Model. However all my attempts resulted in error stating on one hand,
"feature execution failed, non manifold body extracted"
and on the other hand,
"feature execution failed, substractbodies: substract will produce non manifold body"
can you help me with a step by step method of dealing with these two scenarios so as to obtain the fluid domain.

Also what are the steps for dealing with free edges and non-manifold edges and vertices