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-   -   FSI with time interval remeshing ? (http://www.cfd-online.com/Forums/cfx/64997-fsi-time-interval-remeshing.html)

realanony87 May 31, 2009 20:43

FSI with time interval remeshing ?
 
Hello,
I am doing a transient FSI simulation of a wing with Ansys Simulation in Workbench and CFX. and due to large deflections (the same order as the length), the mesh quality gets poorer with each time interval.
Is there a way that I can Remesh the region around the wing instead of relying on the mesh interpolator, every X time intervals ? It seems to have been done in the literature with in-house codes but Is there a relatively easy way to do it in the Ansys Suite ?
Thanks

mortazavi June 1, 2009 04:53

hi realanony87:)
sorry I don't know the answer,but :
would you please help me with the error"the connection between cfx and external solver has died unexpectedly" in FSI modeling in CFX????
what does this error means & how can i solve this problem?

realanony87 June 1, 2009 08:33

It is probably due to an error from the Structural solver. Check the .out file from Ansys ( not the CFX out file) to see what went wrong. I cannot help you because it could happen due to many reasons.

stumpy June 2, 2009 19:59

Remeshing + FSI is not currently possible with ANSYS + CFX. But there's a lots of ways to maintain mesh quality for large deflections. Using a mesh stiffness of "Increase Near Boundaries" with an exponent of say 2 would be a starting point. Then you need to look at where the mesh is folding - and change the mesh motion boundary conditions, or add subdomain mesh motion, or insert sliding interfaces etc to imporve things. Sorry i can't be more specific; the best approach is always case dependent.

Vinzent September 14, 2010 05:32

different mesh stiffnesses of subdomains
 
Hello,

to play with mesh stiffness is very usefuel in case of large deflections. How is it possible, to define different mesh stiffnesses of subdomains? I just know this for a whole domain. So I have to control these complicated with if statements. Is there an easier way?

Vinzent

stumpy September 14, 2010 09:04

To get a different mesh stiffness in a subdomain you will need if() statements, but the inside()@ function should make this fairly easy, e.g.
if(inside()@subdomain1, meshstiffness1, meshstiffness2)

Vinzent September 14, 2010 10:11

stumpy, thank you very much!
this is, what i was searching for.

vinzent

Vinzent September 17, 2010 07:29

Hello Stumpy,

when I try to define mesh stiffness with "inside" like your example following error occurs:

##############################################
Error processing expression 'Mesh Stiffness'. Error at position 4. The condition expression in 'if' statement is not logical valued.
Error processing expression: Mesh Stiffness = MS

##############################################


Is there something missing?


Vinzent

stumpy September 17, 2010 12:04

The inside() function returns 0 or 1 - I was assuming this was enough for CFX to evaluate if it's true of false, but perhaps not. Try if(inside()@subdomain1 > 0.5, ....


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