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Originally Posted by julien.decharentenay
Thanks a lot for the info. I seem to understand that your best practice are derived from experience, rather than taken from literature - although most looks pretty much common sense. Is this correct?
A quick question on the Ahmed body. My understanding is that the measurements are focused on the pressure in the rear body (particularly on flow field vs rear angle and flow detachment). How are you fining correlation between k-omega SST and experiment? I was under the impression that the "standard" was linear k-epsilon with non-equilibrium wall function. What is your experience?
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More or less yes. But some of the info from working with my professor was from literature also. I used a both approaches as there is no set in stone best way to set up since all cases are different.
Yes the Ahmed body is to study the separation of flow on the "hatch"/slant of the bluff body. It is also good way to study the wake. You are correct in saying that the the k-epsilon is considered standard and it also correlates better to the windtunnel data from the ahmed study. In most cases I ran with different turbulance models, k-epsilon showed a slightly higher drag and lift value. This correlated closer to the actual measured drag and lift.
After that, you might be wondering then why I don't use k-epsilon. The reason is from talking to more experience people than myself about its correlation to real world motorsports cases. I discussed this in detail with one. Basically they noticed that the k-omega sst model worked better in cases with high separation. Since most actual cars and racecars have a good amount of separation of flow, it usually is gets better results. ***Other people will disagree however since I know many who still use k-epsilon*** Also remember, it is just a mathematical model to represent the chaos that is turbulence.