When I went through the training, they explained the process but I have never used it. It was quite complicated to do it for Inventor files. I can't find anything in my notes, but I seem to recall that it involved workplanes and derived surfaces. The easy way to simulate the 2D analysis is to make a thin slice .001 thick or so. It is not quite as fast as 2D because it does have depth, but it is easier than trying to get 2D geometry out of Inventor. If you really need to do a 2D analysis, try talking to your VAR or checking the CFDesign forums-- One of them should be able to help.
Dan