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

RAM and Processor

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

Like Tree2Likes
  • 1 Post By CapSizer
  • 1 Post By CapSizer

Reply
 
LinkBack Thread Tools Display Modes
Old   May 31, 2013, 03:51
Question RAM and Processor
  #1
Member
 
Adhikar Hariram
Join Date: Dec 2012
Location: South Africa
Posts: 40
Rep Power: 3
PedFr0 is on a distinguished road
Hello all

I am currently in need of a pc to use for FLUENT and would like some help on the issues regarding the RAM and processor capabilities:
1) If i were to use standard RANS turbulence models in double precision and had 16/32GB of ram, approximately how large a mesh could I solve?
2) Does the processor affect the size of problem that can be solved or merely the time it will take to solve, so for example, I could have 20million cells and solve on a dual core processor, but it would just take impractically long?
3) As far as the scale of the problem is concerned, would RAM or the processor be of more importance?

Thanks in advance
PedFr0 is offline   Reply With Quote

Old   June 2, 2013, 12:03
Default
  #2
Senior Member
 
Charles
Join Date: Apr 2009
Posts: 173
Rep Power: 8
CapSizer is on a distinguished road
1. It depends. The coupled solvers need more memory than the segregated ones. Around 1 million cells / GB is a handy rule of thumb, but that is for single precision. Double precision coupled compressible could need up to 4 GB / million, but that is just a thumbsuck. I think hexa cells may need more memory than tetra (8 nodes vs. 4 per cell).
2. Correct, problem size is independent of CPU, provided that you have lots of time.
3. RAM.
PedFr0 likes this.
CapSizer is offline   Reply With Quote

Old   June 2, 2013, 12:42
Default
  #3
Member
 
Adhikar Hariram
Join Date: Dec 2012
Location: South Africa
Posts: 40
Rep Power: 3
PedFr0 is on a distinguished road
I appreciate the response, and just in time as I can order my system tomorrow. I may just use single precision to allow for larger models. Thanks
PedFr0 is offline   Reply With Quote

Old   June 3, 2013, 02:42
Default
  #4
New Member
 
CFD
Join Date: Jan 2013
Posts: 23
Rep Power: 3
siefdi is on a distinguished road
Hi All,

I have a sort question (again)?

Coming to the RAM, does ECC is that important in CFD?
I did some reasearch which succesfully confused me; some people says 'yes' while some other says 'no'.

Thanks a lot,
Regards,
siefdi
siefdi is offline   Reply With Quote

Old   June 3, 2013, 04:58
Default
  #5
Senior Member
 
Charles
Join Date: Apr 2009
Posts: 173
Rep Power: 8
CapSizer is on a distinguished road
Quote:
Originally Posted by siefdi View Post
Hi All,
Coming to the RAM, does ECC is that important in CFD?
Check the motherboard specification. Dual-socket boards tend to require ECC, especially above a certain size. Single socket boards don't. In my experience of running CFD on single socket boards. it is not necessary to use ECC memory. I've seen no issues that could be attributed to not using ECC memory, but it would be interesting to hear what others have experienced.


There is an advantage to using normal RAM, in the sense that you can get faster memory (if your board supports it). It is possible to buy cheap, poor quality ECC modules, and these are to be avoided. If you buy quality brand name modules, you will be far less likely to have reliability issues. Brands that I know are satisfactory are Kingston and Crucial. There are other good ones out there as well.
CapSizer is offline   Reply With Quote

Old   June 5, 2013, 04:41
Default
  #6
Member
 
Adhikar Hariram
Join Date: Dec 2012
Location: South Africa
Posts: 40
Rep Power: 3
PedFr0 is on a distinguished road
While this thread is still receiving some attention, I would also like to get your opinion as to which is better, an entry level proffessional GPU, such as a quadro k600, or a mid-level gaming GPU, such as an Nvidia TX650Ti. I know that it only plays a role in the extraction of results, but less lag is always better.
PedFr0 is offline   Reply With Quote

Old   June 5, 2013, 10:45
Default
  #7
Senior Member
 
Erik
Join Date: Feb 2011
Location: Earth (Land portion)
Posts: 439
Rep Power: 8
evcelica is on a distinguished road
I don't think it plays a role in extraction of results. That's usually a hard drive operation.
evcelica is offline   Reply With Quote

Old   June 5, 2013, 10:50
Default
  #8
Member
 
Adhikar Hariram
Join Date: Dec 2012
Location: South Africa
Posts: 40
Rep Power: 3
PedFr0 is on a distinguished road
In terms of contour plots and pathlines though, won't the GPU make a difference with regards to that?
PedFr0 is offline   Reply With Quote

Old   June 5, 2013, 13:32
Default
  #9
Senior Member
 
Charles
Join Date: Apr 2009
Posts: 173
Rep Power: 8
CapSizer is on a distinguished road
I've had to ask myself this question a few times when putting together a new machine, and decided that for the kind of work that I was doing (< 15 million cells) I was better off spending the extra money on better or more memory, rather than on a "pro" graphics card. I'm not sure of that is right though. I've seen marketing material from Ansys showing screen images with obvious problems on a gamer's card, compared to the correct image from a certified pro card. Also, I understand that although some of the Ansys suite of programs can benefit performance-wise from the GPGPU, it has to be a Quadro rather than a GeForce.

I've also picked up difficulties with GUI instability when trying to use StarCCM+ with an ATI/AMD Radeon card, yet it worked fine with all my Nvidia GeForce cards. Perhaps it would have been OK with an ATI/AMD Fire Pro card? Dunno, didn't have one to test.

FWIW, I also have a compact "cheap" perpetually upgraded machine that has done much productive work for me, on grids of up to 12 million cells. Currently this just has the built-in Radeon graphics processor (no separate graphics card), and it still manages to do most of the required post-processing without too much difficulty.

I guess it partly depends on how demanding your graphics post-processing is likely to be, but it looks to me as if you only really need very heavyweight graphics equipment if you are dealing with larger data sets.
PedFr0 likes this.
CapSizer is offline   Reply With Quote

Old   June 6, 2013, 07:22
Default
  #10
Member
 
Adhikar Hariram
Join Date: Dec 2012
Location: South Africa
Posts: 40
Rep Power: 3
PedFr0 is on a distinguished road
Thanks a ton CapSizer, your help has been extremely valuable to me, and from what I can tell, better to be safe and go with a pro graphics option.
PedFr0 is offline   Reply With Quote

Reply

Tags
fluent, hardware, mesh, processor, ram

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to create large Mesh? pkr OpenFOAM Native Meshers: blockMesh 14 April 22, 2013 13:18
Graphics card or Processor for Fluent PedFr0 Hardware 5 March 25, 2013 13:29
Fluent uses too much RAM Komon FLUENT 0 December 11, 2011 11:10
CFX11 + Fortran compiler ? Mohan CFX 20 March 30, 2011 18:56
Superlinear speedup in OpenFOAM 13 msrinath80 OpenFOAM Running, Solving & CFD 17 August 22, 2009 03:59


All times are GMT -4. The time now is 02:45.