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-   -   [ICEM] Other Ideas or how would you do it ? (http://www.cfd-online.com/Forums/ansys-meshing/100077-other-ideas-how-would-you-do.html)

diamondx April 19, 2012 12:59

Other Ideas or how would you do it ?
 
5 Attachment(s)
Hello everyone,
Not sure if this thread should be in the meshing section or fluent section since i discuss both but i want more opinion about the meshing
I've finally finished the meshing for my supersonic air intake. I already talked about it previously. sorry to bring it up again.
As you can see in the screen shots below. When i imported my geometry in ICEM. I splitted it in three parts: BACK , INSIDE, and FRONT.
the BACK part and the FRONT were quite difficult to mesh using a hexa mesh so i went for a tetra.
The inside was meshed in HEXA.
The three part were after merged in Fluent by using interfaces, in the front and the back.
My flow is supersonic (mach number=2.5) , i had a lot of trouble converging as the residuals get stuck around between 1e-02 and 1e-03.
And i also got the time stepping warning but the solutiong doesn't seems to diverge
i started with a courant number of 0.1 and very low under-relaxation factors which i was changing to higher value i soon as i noticed a stability. i also changed the positivity rate limits to 0.05 because of the high speed flow.
Do you think that convergence and the warning are due to the interfaces or may be because fluent is running is parallel ?
Will you split this geometry in three if you were to perform the meshing ? i know high speed flow with shocks are difficult to converge, just looking for others opinion and ideas.
Is a minimum of 0.6 in the skewness for the front and back good to use in Fluent ?

Thanks a lot for your helps.

diamondx May 22, 2012 14:52

Tutorial on hexa meshing
 
hello,
I'm back again :o
I managed to mesh the geometry entirely in hexa.
http://dl.dropbox.com/u/35161486/hole_intake_hexa.png


I decided to make a tutorial about it. There will be 4 or 5 part in the tutorial.
I am not a professional, so i invite everybody to comment and to propose if there are any easier ways... you are welcome.
some geometry cleaning are featured in the beginning. Meshing is easy, the back is a little bit tricky if you are a beginner (i had trouble to come up with a blocking strategy, i gave up and used tetra instead. while i got more familiar with hexa meshing i came back to it and could do it.). but otherwise i merged blocks and extruded a lot.
Here is Part I and Part II
PART I: http://www.youtube.com/watch?v=7WF8niG1suM
PART II: http://www.youtube.com/watch?v=MS3GcUGHs_4

Other part are still in the making...
Thanks for any feedback

Far May 22, 2012 15:16

Nice work. I am also thinking to add voice to tutorials, but I am afraid of my English accent (Pakistani accent)

This intake is with 8 holes, you have previously mentioned in some post?.

Far May 22, 2012 15:22

Quote:

i started with a courant number of 0.1 and very low under-relaxation factors which i was changing to higher value i soon as i noticed a stability. i also changed the positivity rate limits to 0.05 because of the high speed flow.
Do you think that convergence and the warning are due to the interfaces or may be because fluent is running is parallel ?
Are you using density based solver? Use solution steering it will automate the process of changing courant number.


Quote:

Will you split this geometry in three if you were to perform the meshing ? i know high speed flow with shocks are difficult to converge, just looking for others opinion and ideas.
If it is difficult then I may also go for this option. But keep in mind that the shock waves are very much sensitive to mesh resolution and interfaces may be lethal to it.

Quote:

Is a minimum of 0.6 in the skewness for the front and back good to use in Fluent ?
This is good quality, but problem may be the mesh requirements in shock waves area

diamondx May 23, 2012 12:28

more tutorials
 
Thanks FAR for the advices.
I talked more about my convergences problems in this fluent thread:
http://www.cfd-online.com/Forums/flu...nvergence.html

I just finished Part III today, here's is the link:
http://www.youtube.com/watch?v=nuiRkZqaEz4

Thanks again


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