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keith gray December 13, 1999 02:21

extent of user control?
I am an avid user of CFX and would like to cross over to Fluent, as it is much more user friendly on the interface end. There are certain things I need as far as control of the model is concerned, however: I need to be able to vary the boundary conditions periodically in time, and the same with the grid geometry. I also need to be able to post process by looking at each timestep to watch the unsteady flow develop in time. I have been doing these in CFX via user Fortran subroutines- are there means for accomplishing these in Fluent?

Jonas Larsson December 13, 1999 04:28

Re: extent of user control?
Fluent does not support moving meshes yet, so modifying the grid during a simulation is probably going to be difficult to do correctly. This is coming in version 6 though, but 6.0 isn't due out until late 2000 I think. Time-varying boundary conditions are easily done with a UDF in the current 5.2 version. UDF's are a bit tricky to write though - the doucumentation is far from complete, but the time-varying boundary condition is one of the few UDF examples that Fluent has available. Post-processing is also no problem - you can easily generate movies etc. that will show you the time-evolution.

Sung-Eun Kim December 13, 1999 16:21

Re: extent of user control?
You can either use user-defined functions (UDF) or rely upon standard interface. to specify time-varying boundary conditions. UDFs allow you to specify =transient BCs using any arbitrary functions. Alternatively, you can write a BC "profile" file in advance containing boundary values vs. time (Please see the FLUENT 5 user's guide addendum on our user-service center)and can read it into solver via standard user-interface. If BCs are periodic, you can make them repeat themselves.

Regarding the mesh, FLUENT 4.5 curently as same capability as in CFX.

Jan Rusås December 20, 1999 08:34

Re: extent of user control?
You write it is possible to have a function as inlet, is it also possible to have the values at discrete points or at cell centres?

You wrote:

Regarding the mesh, FLUENT 4.5 curently as same capability as in CFX

Does that mean it is possible to have a grid that vary in time, in fluent?



Amadou Sowe December 20, 1999 11:28

Re: extent of user control?
It is not very clear as to what you mean by saying that Fluent 4.5 has the same capability as CFX. In terms of the grid, I thought that CFX uses multi-block approach and Fluent 4.5 (structured) used single-block.

Sung-Eun Kim December 20, 1999 11:58

Re: extent of user control?
Admittedly I wasn't clear. What I meant was: In terms of the usage and functionality of "moving/deforming" mesh, FLUENT 4.5 would be similar to what CFX offers. The original question was regarding moving/deforming mesh capability and that's probably why I did not put the modifier"moving/deforming".

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