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-   -   Multiphase in CFX4 and CFX5 (http://www.cfd-online.com/Forums/cfx/20728-multiphase-cfx4-cfx5.html)

 Anne October 19, 2004 03:47

Multiphase in CFX4 and CFX5

Hi all,

Could some one please share with me their multiphase simulation experience with CFX4 and CFX5 (let us consider the latest of both, CFX4.4 and CFX5.7).

I am simulating a solid-liquid system in a stirred tank using same simulation stategy in both CFX5.7 and CFX4.4. I have got 172k cells in CFX4.4 and 526k cells in CFX5.7 in same geometry size. Before I prempt anybody's objective opinion, let me ask, has any body noticed any significant (more than 80%) difference?

Or am I just comparing apples (structured grid) and oranges (unstructured grid)?

regards Anne

 jon October 19, 2004 05:35

Re: Multiphase in CFX4 and CFX5

check out the number of nodes.

 Anne October 19, 2004 09:52

Re: Multiphase in CFX4 and CFX5

Okay, let me give specific figures now: CFX4.4 cells = 199,888 nodes = 29,640 CFX5.7 cells = 525,276 nodes = 98,672

thanks Anne

 Stevie Wonder October 19, 2004 10:37

Re: Multiphase in CFX4 and CFX5

Why don't you import the CFX-4 (.geo) and run in your CFX-5 (load it into PRE) and check the results?

 Anne October 19, 2004 12:07

Re: Multiphase in CFX4 and CFX5

Hi Stevie,

That was the most obvious thing to do, but there were some limitation as far as the model importation from CFX4.4 to CFX5.7 was concerned. That is already an explored area with the cfx support. Thanks for the suggestion.

regards Anne

 Stevie Wonder October 19, 2004 14:01

Re: Multiphase in CFX4 and CFX5

I meant that you could use the same grid for both codes. This way you could trace the main differences between the models implemented within the codes, not using an hexaedral mesh for one code and a hybrid mesh for another one, i.e., comparing bananas and watermelons in my point of view.

 jon October 20, 2004 04:36

Re: Multiphase in CFX4 and CFX5

The nodes and cells should be the same (approx.) for cfx4.

 Anne October 20, 2004 04:51

Re: Multiphase in CFX4 and CFX5

Hi Jon,

You are right, CFX4.4 is based on a structured grid. I forgot to put is this way; CFX4.4 cells = 199,888 BOUNDARY nodes = 29,640. You may well just ignore the boundary nodes as i guess they may not be critical for the present discussion as they have a differnt meanig to the CFX5 nodes.

regards Anne

 Neale October 30, 2004 21:20

Re: Multiphase in CFX4 and CFX5

Anne,

As "Stevie" mentioned, on the same grid, with exactly the same problem setup, with decent convergence levels, the two codes should give fairly similar answers.

They will never give the same answers as they are two completely different flow solvers, eg: CFX-4 is uncoupled/cell centered, CFX-5 is coupled/cell-vertex.

Exactly why can't you import your CFX-4 grid? This should be possible for sure.

Neale.

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