I am currently trying to make a cut out of my model INSIDE the solid box, however, I am currently having a problem as it keeps saying that they’re not intersecting as seen in the image below.
for rhino those objects are just floating one inside another. if you want to make a difference, yo have to divide the box in half. the intersection is between surfaces, not the volume inside
If your CFD software takes meshes, mesh both the box and the hull, flip the direction of the hull and join the two meshes - that’ll give you a solid mesh with a void; then export in a mesh based format.