CFD Online Discussion Forums

CFD Online Discussion Forums (
-   CFX (
-   -   Limit in Number of Simple Constraints (

Luis Rojas-Solorzano September 11, 2002 13:25

Limit in Number of Simple Constraints

I'm trying to set up a simulation which, because of the complexity of the geometry, requires 5000 Blocks and aprox. 600 constraints.

At this point, the pre-processor meshes a small model with sample constraints, similar to those in the large-scale model.

However, when I try to set up the constraints within the pre-processor for the large-scale model, it takes about 412 MB just re-organizing the constraints and stops with the following error: "unable to process list of Nodes..."

Although my machine has about 800 MB ram, I'm wondering if there is a limitation in the number of constraints that can be handled by the pre-processor software, besides that limited by the ram and HD capacity of the machine.

Any help will be highly appreciated. Regards,


cfd guy September 12, 2002 08:30

Re: Limit in Number of Simple Constraints
Hi Luis,
I'll assume that you're using CFX-4. I'm afraid that you won't be able to run your case even if you finish your mesh in the pre-processor. Once I've built a mesh, that didn't contain very large number of elements, actually less than 600k, but it contained over 2500 blocks. I could not run this mesh in our workstation with 2 Gb of RAM. I had to import this mesh and run it on CFX-5.
Regards, cfd guy

Astrid September 12, 2002 16:52

Re: Limit in Number of Simple Constraints
What type of problem requires 5000 blocks?? Like 'cfd guy', I strongly suggest to hop over to CFX 5.5.1, at east, if you do not require the models of CFX 4 (radiation f.i.).

Perhaps CFX-Hexa (or ICEM CFD) can do the job, although I don't know its limitations in number of blocks.


cfd guy September 13, 2002 07:53

Re: Limit in Number of Simple Constraints
Hi Astrid,
The problem I mentioned was a burner within a rotary kiln furnace. The burner layout was very complex and demanded a lot of blocks. I used ICEM HEXA to build its mesh but somehow I couldn't merge the blocks, that's the reason why I could not run in CFX-4. I believe ICEM doesn't have a limitation about the number of blocks.

Luis Rojas-Solorzano September 13, 2002 10:48

Re: Limit in Number of Simple Constraints
Hi Guys,

The problem I'm running is the propagation of contaminants within a two-way inter-connected car tunnel, 1 mile-long,not straight-shaped precisely, with lots of ventilation windows on different parts of the roof and several sidewall extraction galeries.

The geometry includes the cars inside the tunnel when a traffic jam sets in and also includes their exhaust pipes, for the most real simulation of the hydrodynamic emission conditions.

I'm starting to get to know CFX5 and very probably will migrate the case from CFX4 to CFX5 within the next days. Regards and thanks for all the hints.


Dave September 16, 2002 08:22

Re: Limit in Number of Simple Constraints
Luis if you do migrate to CFX5 then do not get rid of your old CFX4 geometry as with a little tidying up you will be able to use it in CFX5. Dave

Luis Rojas-Solorzano September 18, 2002 09:30

Re: Limit in Number of Simple Constraints
Dave, thanks for the hint. Actually we've started migrating the geometry file and, in fact, a good deal of the previous geometry (CFX4) can be used in the CFX5 geometry builder after imported.



All times are GMT -4. The time now is 15:23.