I'm interested in finding a 3d aerodynamic analysis program for drag determination on relatively simple automotive body shapes. I am interested in seeing effects of varying base size, fastback angles, etc. on shapes that are very clean. I have a 2d program for airfoils that was inexpensive (< $100US) that correlates well with tunnel data. Id like to find a 3d equivalent for simple shapes. Any suggestions?

Well, OpenFOAM (http://www.openfoam.org) is free (public domain) and it will do the job you mention without trouble.

Hrv

Thanks. I am hoping to find something that will run under Windows 2000, and that is somewhat simpler than OpenFOAM(albeit less versatile) to use for someone who is virtually illiterate in the CFD world. In the best of all worlds, I could change a car body shape interactively, to see the effect of a bump or a mirror or a spoiler here or there. After the shape was optimized, I could export the optimized shape back into the CAD program that was originally used to create it. Am I dreaming?

Basically yes, you are dreaming. Especially at your price point. Some of the relatively new "CAD-integrated" CFD codes could probably help you here, but they are not exactly dirt cheap. You would still need to know what you are doing, in aerodynamic terms.

as u deal with optimization (automatic design) u can add optimizatin feature (adjoint sensitivity analysis) to your selection option (some code has this option)

www.dofyn.net shows screenshots around cars. It is a still-young code, not as powerful as OpenFOAM, but, given your requirements, it might be good for you.

Perfect! Many thanks Jojo. (The link wouldn't work, but I added an l in what I guessed to be the right place, and sure enough...)