Could you please elaborate on what is the objective of this analysis? Do you wish to perform an external flow aerodynamic analysis? That being the case then there are various changes to be made to the geometry and mesh.
The CAD model should be a solid structure, and not shell, to generate a hex-dominant mesh. Since there are discontinuities the mesh generation is not in the region expected. Kindly make sure to import solid geometry, preferably as a single solid.
For external flow analysis, especially for compressible case, the domain should be large enough to allow for density changes, in absence the which the solver diverges. As a thumb rule the domain should be 3 to 5 times and 8 to 10 times the dimension of the geometry, upstream and downstream respectively. The Formula Student SAE workshop can be referred for setting up the case. The Hex-dominant parametric mesh can be generated to define refinements wherever necessary.
The simulation setup should be straight forward once you get an appropriate mesh.