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Prakash.Paudel August 12, 2010 12:07

few quesions on ANSYS ICEMCFD and FLUENT
Hi Simon and everyone

I didnot write in a public thread because i was not sure if my questions would be answered by anyone and esp.. by you. Thanks for taking time to answer my questions . I will keep your words in mind while making sure my mesh is good enough.
With regards to Slip boundary condition, how would you specify slip in fluent . I know there is an option for no-slip in fluent when you edit wall boundary condition. Do you specify slip by specifying shear conditions?? and how would you determine the shear conditions? Is there a way to specify slip by specifying slip velocity?
Any ideas from anyone would be highly appreciated.

And ya Simon, Toronto must have changed a lot since you left. I came here 4 yrs ago and i go to school right on Gerard street. I guess when you were here it was called Ryerson Polytechnic Institute but they transformed it into a University now. I love Toronto and i think i will be here few more years.


Hey Prakash, I lived in down town T.O. for 4 years (1995 thru 1999). I loved it there. I was one block from Young Street on Gerrard St. I still miss the hotdog vendors and the warm early springs due to the "heat island" effect of such a big city.

In future, these questions should be thru a public thread so I can justify my time to answer them. Perhaps you could post these questions and answers for the benefit of others?

Anyway... 1) not my area, ask a Fluent person. Usually, I just specify no slip or slip, I have not played much with the in between. Unless you are talking about wall roughness?

2) These min criteria vary from solver to solver and vary by mesh type. For ICEM CFD hexa in Fluent, try to get a Min angle above 18 with only a few elements (or none) between 9 and 18 degrees. You don't want elements below 9 degrees, but sometimes it happens and I run it anyway. You want the Determinant above 0.1, but again, a few below will still run. That is all I usually check, but the Fluent manual will state more. Note; the Fluent manual will be talking about TGrid Skew, you can find that particular metric in the list. The manual tends to be conservative (higher requirements than actually necessary), just to blame the mesher if something goes wrong ;) Also note that 13.0 will come out with a new metric developed in a collaboration between Fluent and CFX experts. This "Orthogonal Quality" metric will provide the best way to evaluate your mesh before solving.

3) Unstructured is about the way the nodes are stored... You can have a very nice unstructured Hexa mesh created from ICEM CFD Hexa. This is what Fluent 6 (or 12) wants and what you should provide. Older versions of Fluent required Structured mesh, but it has been a while since I did that for Fluent. To output Structured Multi-block mesh, right click on "Premesh" and you will see the option.

Have fun.


Originally Posted by Prakash.Paudel
Hi Simon!

Your youtube video of 2d airfoil was very valuable to me to start learning hexa-meshing in Icemcfd. I am an undergraduate student and i am learning Icemcfd and fluent this summer so i don't have to work so hard on it when i have to actually use it during the fall session.
I am new to this online cfd community but i have noticed in this 2 months that you have been very helpful to so many people working with cfd. I was wondering if you could help me with some project that i am doing.

Its a very simple project. Its a 2 D axisymmetric model of a cylindrical pipe with an aneurysm somewhere in the middle. I have created a geometry and mesh and exported it to fluent v12.1.2 ( i guess v6.4 is v12.1.2 ? ) after 2-3 months of working with Icemcfd and fluent. I implemented translational periodic boundary condition and specified the mass flow rate to impose fully developed velocity profile at the inlet.I have successfully implemented no-slip boundary conditions at the wall. Now,

1/ I want to implement different slip conditions by specifying slip velocity.

2/ I want to know if my mesh passes the quality test. what are the minimum criteria?

3/ i want to know if fluent 12.1.2 only supports unstructured mesh ? if it does support structured mesh, which one do you think is appropriate in my case . And if structured mesh is the one i should be going for, then how do i do it ??

i guess thats enough questions for the first email. :) I would really appreciate it if you could answer these questions as soon as possible. And if you need to see my geometry and mesh and anything else, i would gladly send them to you.

Thanks much and I hope you have a very nice weekend

Prakash Paudel
Toronto, Canada

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