If you are given production-ready detailed CAD geometry (nuts, bolts, and all) for Computational Fluid Dynamics (CFD) analysis you have to ask yourself, is this really an engineering endeavor or a marketing exercise? Given the effort to produce a complete, detailed CAD model, it is unlikely that any significant changes will be looked upon favorably. Instead you will likely find that CFD is to be used in its weakest form, i.e., Colorful Fluid Dynamics (CFD) for marketing.

Weak Form CFD for Complex GeometryAirflow around Tower Bridge

Marketing CFD has its place, but it's useful to know that this is the goal prior to wrestling with a complex CAD model, so that you are aware the geometry and the simulation can be compromised to make the colorful graphics easier to generate.

Strong Form CFD for Simple GeometryAirflow through a cyclone

If you find yourself asked to perform CFD early in the project life cycle (ideally during the concept design phase) on relatively simple geometry, then you know that CFD is being used in its strongest form, i.e., as a guide for real product decisions. This is a moment to savor and bring the full power of your CFD skills combined with your engineering knowledge to bear on the problem at hand, so don't just lean in - dive in!