Anyone know of any decent aerodynamic simulation programs?

I’m looking for a program that will take CAD drawing and simulate how are moves around it. This is for a CO2 dragster design if you’re wondering. Anyway, I intend to use Autodesk Inventor (or something else by Autodesk) to make one 3D .ipt part.

From here I need a program that will take the shape of the part and simulate how air moves around it. Even if airflow wouldn’t effect the speed of my dragster much I would still like to experiment with the concept. Also, this being mostly out of curiosity, I need this software to be free (or very cheap).

So anyone have an idea of an aerodynamic simulation program that meets these reqirements?