Hello does anybody has experience on computations of development length in turbulent pipe flows (after a sudden contraction or expansion) with commercial CFD programs using RANS approach?

I see people in CFD community people compute very complicated problems in daily life and most of them never computed such a simple configuration in order to check the performance of a model. Any input or reference on this topic will deeply be appreciated.

"What do we know about turbulent pipe flows?"

I recently attended a seminar on new trends in CFD.

Here Milovan Peric (Co-author of Computational Methods for Fluid Dynamics and CD-Adapco employed) gave an interesting speach on the subject.

He also answered a similar question as yours! His answer was that the CFD codes almost always have dificulties when dealing with very simple geometry like and airfoil or spheres or your pipeflow. In contrast the CFD codes dealt very good with complicated geometries with sharp corners, edges and alike. He had results with bad geometries that was spot on experimental results.

In the end there was a panel discussion with represents from Ansys, CD-adapco, openFoam. This was very interesting

Best Regards Kasper

Seems not plausible that a model can not predict well simple flows but much more complicated flows.

In my opinion, in case of a simple geometries we do know quite a lot about the flows from experimental data, DNS/LES and analytical considerations. However, for the complicated cases, references (with whom CFD data is compared) themselves are not as accurate and detailed as in the case of simple flows e.g. pipe flow.

Still I am interested in Prof. Peric's presentation on this topic. Do you have this presentation with you or some exact details of the presentation so that I can write to him directly?

many thanks

Hello, i am also interested in this seminar , if u have please the presentation or know how can i get the presentation , I would appreciate your help . my email is written in the upper case thnaks

I will post a link here once the presentations are ready. But I have to remind you that the seminar was on Future Trends in CFD. The bad/good geometry question was a seperate question not included in any of the presentations. But you can still write him, i guess his email is milovan.peric@de.cd-adapco.com

I once compared the computed development length behind a reduction (not sudden) against experiments. The results were not very good. I think it is because there were very low levels of turbulence downstream the nozzle and there is a turbulence transition which was not accounted for properly. I think the development length depends strongly on initial conditions and "perfectness" of the pipe in terms of smoothness, straightness, and small imperfections which can lead to strong changes for the developing flow. So the comparison with any published data is really useless if these things are not documented. I am in search for a paper that adressess these influences experimentally. I also thought of doing some experimental investigations in our lab.