Learning Forum

[Gregory Harrington]

I am using Fluent on my company's virtual machine that has specs of Intel(R) Xeon(R) CPU E5-2683 v4 @ 2.10GHz   2.10 GHz  (2 processors) and 128 GB of RAM.

I have a 29M cell polyhedra flow model. The model completed hybrid initialization but never finishes one iteration of the solution. 

I opened the task manager to see if the machine is out of RAM but 91% CPU and 64 - 80 GB of RAM. The virtual machine has more than enough RAM to solve a model of this sizewhen using a SIMPLE solver.

What could be the issue?

[Gregory Harrington]

I should also add the virtual machine was able to solve a 26M cell model the other day until I added some additional computational volumes to the model

[Rob]

Were any other settings changed along with the addition of the extra volumes? 

[Gregory Harrington]

Hi Rob, Thanks for the quick response, I checked the other settings and it turns out the newer model was defaulted to coupled solver and the previous model that ran fine was set to SIMPLE. I am now running the newer model that has 29M cells and it is running fine but it us using ~120 GB of RAM. That means even with a pressure based SIMPLE solver with polyhedra cells it's using 4GB/1M cells which seems like a lot.

I thought the recent Fluent versions only use 1-2 GB/1M cells. Do you think it's any issue with my hardware or the fluent parallel settings?

[Rob]

SIMPLE is generally 1-2 GB /1M cells, but I'd expect on the higher end with poly cells. PBCS will be nearer 3-4GB/1M cells as the pressure & velocity are coupled.  Depending on other models etc you may be using more RAM. 

Historically it was easier to tell if you were low/out of RAM as the hard drives could be heard spinning up to aid in memory swapping/paging. Ie there was an audible warning and (generally) some panicking from IT. With SSDs everything is nice and quiet, albeit very slow.