CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Hardware

Slow CFD

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 13, 2011, 14:57
Default Slow CFD
  #1
New Member
 
Adrian Dunne
Join Date: Jan 2011
Location: Ireland
Posts: 26
Rep Power: 15
ad281 is on a distinguished road
Hi,
I am a final year Mech. Eng. student performing CFD simulations for my thesis. I am running several versions of a 2D simulation. They are transient and are each taking about 24 hours to solve.
My issue is that, when I look at my computer's performance while running the solver, I can see that only half of the RAM is operating. The solver is taking up over 500MB of RAM, but I'd like it to be able to take up more, to improve computation time.
I know it's not an issue with a slow CPU, as this is running between 50% and 70%.
I use 32-bit architecture, 667Hz and 4GB RAM.
I would appreciate any suggestions on how i can improve compute time.
Thanks.
ad281 is offline   Reply With Quote

Old   January 15, 2011, 05:52
Default
  #2
New Member
 
Shishir
Join Date: Jan 2011
Location: Bangalore
Posts: 5
Rep Power: 15
Adren022 is on a distinguished road
generally limiting the number of process running in the background and using a larger pagefile size should help speed things

but it still depends on the speed/core of your processor...faster the speed less computational time
Adren022 is offline   Reply With Quote

Old   January 15, 2011, 07:43
Default
  #3
New Member
 
Adrian Dunne
Join Date: Jan 2011
Location: Ireland
Posts: 26
Rep Power: 15
ad281 is on a distinguished road
I get what you're saying, but the issue isn't really with trying to procure available memory, it's more to do with the fact that the CPU and RAM are only running at about 50% of their full capacity when running CFD. I want to be able to get the program to take up more RAM and CPU.
ad281 is offline   Reply With Quote

Old   January 15, 2011, 22:12
Default
  #4
Senior Member
 
sail's Avatar
 
Vieri Abolaffio
Join Date: Jul 2010
Location: Always on the move.
Posts: 308
Rep Power: 16
sail is on a distinguished road
wich operative system are you using?

wich is the size of the mesh? are you using multicore paralleling?
sail is offline   Reply With Quote

Old   January 16, 2011, 00:46
Default
  #5
Senior Member
 
Real Name :)
Join Date: Jan 2010
Location: United States
Posts: 192
Rep Power: 16
ComputerGuy is on a distinguished road
Sounds like you're not running parallel. Fluent will grind your machine to a halt, both in terms of RAM and CPU, if you're giving it the necessary resources. Additionally, 32-bit windows can only address 2 GB of the available (almost) 4 gb of RAM, unless the /3GB switch is used in the Boot.ini file.

See the following: http://www.microsoft.com/whdc/system...ae/paemem.mspx

for more info.

ComputerGuy

Quote:
Originally Posted by ad281 View Post
I get what you're saying, but the issue isn't really with trying to procure available memory, it's more to do with the fact that the CPU and RAM are only running at about 50% of their full capacity when running CFD. I want to be able to get the program to take up more RAM and CPU.
ComputerGuy is offline   Reply With Quote

Old   January 16, 2011, 06:47
Default
  #6
New Member
 
Adrian Dunne
Join Date: Jan 2011
Location: Ireland
Posts: 26
Rep Power: 15
ad281 is on a distinguished road
Quote:
Originally Posted by sail View Post
wich operative system are you using?

wich is the size of the mesh? are you using multicore paralleling?
What do you mean by operative system? Like the programme? I'm using ANSYS-CFX.
The mesh is generally around 200,000-300,000 nodes.
I'm actually doing the simulations on my own HP pavillion laptop, it has only a single-core processor.
ad281 is offline   Reply With Quote

Old   January 20, 2011, 17:40
Default
  #7
Senior Member
 
Dave
Join Date: Jul 2010
Posts: 100
Rep Power: 15
daveatstyacht is on a distinguished road
In answer to your question, the operating system would be the overarching system your computer is using. Examples would include windows (xp, vista, 7, etc), Linux operating systems like Debian, Ubuntu, Fedora. It sounds like you are using windows if you are using CFX on single core. As an aside I have found that when programs try and exceed the memory usage limit of a 32 bit windows OS, it tends to crash the program or windows.
daveatstyacht is offline   Reply With Quote

Old   January 28, 2011, 21:23
Default
  #8
Member
 
Join Date: Feb 2010
Location: Australia
Posts: 65
Rep Power: 16
RossFS is on a distinguished road
Quote:
Originally Posted by ad281 View Post
'm using ANSYS-CFX.
The mesh is generally around 200,000-300,000 nodes.
If the mesh isn't sufficiently large to warrant the use of more RAM, the computer won't use it as it doesn't need it.
Consider reading up on the various settings you can set just before starting the simulation in xref.pdf or xmod.pdf or the like in the ANSYS directory (not in the most logical location).

Another thing to check when running CFX is whether you have a process running called java.exe (via task manager). On our machines at uni (dual core) this process would sit in the background (generated via CFX to run the news updates I think) and gobble around 50% of the total CPU power of the machine. Killing this process off had no ill effect other than making a lot more processing power available.
RossFS is offline   Reply With Quote

Old   January 29, 2011, 10:15
Default
  #9
New Member
 
Adrian Dunne
Join Date: Jan 2011
Location: Ireland
Posts: 26
Rep Power: 15
ad281 is on a distinguished road
That explains it.
Thanks man.
ad281 is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Slow speed CFD Eric Strom FLUENT 0 February 25, 2009 17:53
Where do we go from here? CFD in 2001 John C. Chien Main CFD Forum 36 January 24, 2001 22:10
CFD for fans & blower housings David Carroll Main CFD Forum 8 August 24, 2000 18:25
Since Last June John C. Chien Main CFD Forum 3 July 12, 1999 10:38
Which is better to develop in-house CFD code or to buy a available CFD package. Tareq Al-shaalan Main CFD Forum 10 June 13, 1999 00:27


All times are GMT -4. The time now is 19:39.