You can get predictable and repeatable results but they are unlikely to represent anything like the real world. I put up a thread on MicroCFD. Using that it gives you drag and even lift calculations. It also allows you to scale your object to the correct size. I plots pressure, vorticity, temp, and can plot stream lines.
Note its not free but it has a free 3 day trial. You can work around that if so desired.
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