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Christian Cordeiro May 22, 2003 07:33

Hello, I am having a lot of problems of CPU memory and the solve time in my simulation. My model have the following characteristic:

3 fluids Inlet with equation 1 000 000 elements This model is using 900M of virtual memory and 150M of Ram memory. Is it ok ? I try interpolate this model with other model with less elements and try use initial values but the problem is pass the first interaction. What are the rules to interpolate and to use initial value ? Some suggestion ? What is the best way to build a final model ?

Thank you

zahid May 24, 2003 08:12

Re: Memory
Hi Christian Cordeiro I think you should increase RAM of your PC. Use at least 1 GB RAM. I am using Pentium 4, 1.7 GH processor with 1 GB RAM and its performance is satisfactory. I have not properly understood your second question. What do you mean by 'problem is pass the first interaction'? Please explain so that I can help you. Also mention the software you are using. Best regards.

Christian Cordeiro May 26, 2003 07:37

Re: Memory
Thank you.

Ok, I will increase RAM. I work with the CFX 5.5.1. About the 'problem', when the CFX is solving the simulation, the steps are very slow but I think is because the RAM.

Thank you again.

zxaar May 26, 2003 10:33

Re: Memory
dear people,

i don't know how much it is relevent to this conversation but still i observed it so i am mentioning it.

when i used to work with CFX4.4, i observed for many times that if i stop the iteration and try to give run again. it used to give me some error. in the start i thought i have done some change in command file that these errors are coming. but soon (since i was confident that whatever changes i made are correct) i made conclusion that these errors are because of memory. cfx doesn't release the memory it used in last run, so to handle it what i did is restarted the machine and viola things are running again without error messages. hope this might help somewhere (this helped me a lot , since i knew when it is giving me bogus errors).

Robin May 26, 2003 12:36

Re: Memory
zhaar: This not a problem with CFX-5 and should not be happening with CFX-4 if you shut it down properly.

Christian: CFD is memory intensive. If you are running into swap space you are guaranteed to have problems.


zxaar May 27, 2003 11:15

Re: Memory
well after using it for 2 years (with cfx4.3 and 4.4) i think i understood it how to shutdown properly.

anyway, the prob seems to be with my machine and operating system (or interaction of cfx with OS which was WinNT), but i can't say much since i haven't seen it running on other machines and OS. and when i say it doesn't release memory, it means for the bigger cases (involving more than 200 000 nodes), what i felt is, once the run is given the memory is booked , and when it is over, the memory is not freed properly (it needs good chunk of memory for runnign such case) so if i want to run as bug case again, it may be short of memory (as it used to happen and will not happen for small cases). so to do that i needed restarts (and they used to run next time, without probs).

cfd guy May 28, 2003 06:13

Re: Memory
Swap means Hard Disk Space used to create a virtual memory. If you're running cfd calculations on virtual memory it is expected to obtain very slow solving iterations. Remember, physical memory is much more faster than virtual one. So I'd buy some RAM in your case, or I'd try to use a coarser grid.

Good luck! cfd guy

Nyatoto June 3, 2003 07:49

Re: Memory
Hi cfd guy,

I wonder whether this belongs here... sorry if it doesnt.

What is this bug that holds the memory or canvas window such that the canvas window does not close if the cap lock is on? I have seen it on and off with CFX4.4 Windows NT, however,I have not seen it with CFX5.5.1.

regards nyatoto

cfd guy June 6, 2003 04:49

Re: Memory
Basically was because CFX-4 was compiled in UNIX you needed an Unix emulator to use it, Hummingbird Exceed. Look, it is not a Exceed problem, at least I think so. This Caps Lock bug sure pissed of a lot of CFX-4 customers in the past.

CFX-5 uses QT as GUI, I think. And you can compile it in multiplatforms. That's why you don't have a caps lock bug, but sure you have other ones.

Regards, cfd guy

Nyatoto June 11, 2003 08:12

Re: Memory
Hi cfdguy,

Thanks for that useful information.

regards Nyatoto

hamid-nice May 25, 2016 21:48

changing swap space
how can I set or change amount of swap space in fluent ?
I set page file in windows for 50 Gb

ghorrocks May 25, 2016 22:52

Try the fluent forum. This is the CFX forum.

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