We've been using the beta version of version 12 (mostly for improved polyhedral mesh converion) and it seems to run fairly slow.

Specifically, we have a couple of older Intel machines running Windows. In tests, V 12 beta took about twice as long per iteration as Fluent 6.3. This was both for some fairly generic flows with the serial solver and more complicated models with DPM. I think the solution parameters were set the same, and the results after a fixed number of iterations were about the same.

Anyone else have a similar experience?

Yes the newer versions (6.3 onwards) are slower than previous versions. Because of this reason we are still using older versions. Becuase if the current calculation takes 1.5 months to finish with newer versions it would be more than 2 months for us. After ansys took over Fluent is transforming into CFX, slowly.

I'm no fan of what's becoming of Fluent lately, but I have had an opposite experience. One relatively simple case, all hexa, about 1.2 million cells, was running in 23 seconds per iteration on 6.3 and 20.5 seconds per iteration on 12.0.3. No modification made, just read the case saved from 6.3 into 12.0.3, iterated and compared the performance from that point onwards. Of course, I used the same machine in both runs.

Maybe the grid type had a decisive influence...Although, it shouldn't, this is an unstructured solver, after all.

Razvan