moving boundary in CFX 5.7
 

Can CFX 5.7 simulate the problem with moving (translation)boundary, like piston movement ? If it can be done, Should I mesh the liquid vol. in unstructural tetra grid or structural hexa grid ? Where can I find complete examples or tutorials to learn how to sovle this kind of problems?

Thanks

Gary

Re: moving boundary in CFX 5.7
 

Hi,

CFX Can do the job and there are exactly similar examples avaliable. There is also a tutorial example in CFX-5.7 (Tutorial - 20). If you are still using CFX-5.6 mesh movement is a Beta feature.

You have to create different meshes at different specific positions of the piston and carry out the analysis.

If Tutorial 20 is no sufficient, ask CFX support for the piston movement example which already exists with them

Re: moving boundary in CFX 5.7
 

Thank you very much ! I am trying to contruct a hybrid mesh type now, hexa grid in moving domain and trtra grid in fixed domain . But I can not make sure whether these grids can be moving or not .

Gary

Re: moving boundary in CFX 5.7
 

Hi,

I think you should start by doing yourself Tutorial 20. It has examples of moving and fixed walls, and deformable and stationary meshes.

Regards,

Re: moving boundary in CFX 5.7
 

Hi, I did the tutorial 20, but there was an error when I started solver.

An error has occurred in cfx5solve: The CFX-5 solver could not be started, or exited with return code 255: . No results file has been created.

So did somebody encounter the same problem? How can I continue to finish the tutorial?

Re: moving boundary in CFX 5.7
 

Hi,

This error has been discussed in a previous topic (Error message from moving mesh modelling: http://www.cfd-online.com/Forum/cfx.cgi?read=9065)

It's a bug related to moving mesh. It was introduced with the patch and only occurs in Windows. In Pre, open the command editor, and enter:

FLOW:

EXPERT PARAMETERS:

min mode el = 750

END

END

then click Process

You may also do this editing the CCL file.

If you have access to the CFX Community web site, take a look at: http://www-waterloo.ansys.com/cfxcom...p?TOPIC_ID=629

Regards,

Rui

Re: moving boundary in CFX 5.7
 

Hi,

A better solution to the moving mesh bug is to update to the current version of the code, CFX 5.7.1 which has this bug fixed. Then you don't need to set the expert parameter, and Rui's suggested fix does not work every time anyway.

Glenn Horrocks

Re: moving boundary in CFX 5.7
 

Hi All,

I am also seeing this problem even after I set the parameter

min mode el = 750

values of 300 or 1000 don't seem to help either. I am using CFX 5.7 with service pack 1. When I ask for help about launcher it tells me that I have Version 5.7, 2004.06.28-22.59 (which I think is 5.7.1 ). Is there any other parameter I can tweak to fix this?

Thanks,

Paul.