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

Force fluent to hold only last timestep

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 23, 2014, 12:05
Default Force fluent to hold only last timestep
  #1
New Member
 
Join Date: Feb 2013
Posts: 25
Rep Power: 5
ansys_matt is on a distinguished road
Hello,

I am running a transient flow problem and it seems fluent keeps every timestep in RAM, which eventually causes a out of memory problem. It fills 32 GB holding all the previous timesteps in RAM.

Since there is absolutely NO reason why fluent needs the first timestep in RAM when solving for the 1000th timestep, I would think one could tell ANSYS to only hold say, 5 timesteps at a time. I am already having fluent export the data to a file (under solution activities), but is there any way to tell fluent to NOT hold all timesteps in memory while marching forward in time?

Thanks
ansys_matt is offline   Reply With Quote

Old   August 23, 2014, 20:36
Default Any more active forum?
  #2
New Member
 
Join Date: Feb 2013
Posts: 25
Rep Power: 5
ansys_matt is on a distinguished road
Does anyone know of a more active forum for discussing ansys fluent?

If not, how about somewhere to go where experts help newbs? I have posted 3 times and gotten no response whatsoever!

Thanks!
ansys_matt is offline   Reply With Quote

Old   August 24, 2014, 09:52
Default
  #3
New Member
 
Join Date: Jun 2011
Posts: 22
Rep Power: 7
sescobar is on a distinguished road
Hello,
Based on my experience with Fluent it does not store all the previous time steps in RAM. Depending on your temporal discretization scheme it will store the primitive variables for one or two previous time steps.
What is the set up of your simulation? Number of cells in the mesh? Do you have particles in the flow? How about species and chemical reaction?
sescobar is offline   Reply With Quote

Old   August 24, 2014, 22:07
Default
  #4
New Member
 
Join Date: Feb 2013
Posts: 25
Rep Power: 5
ansys_matt is on a distinguished road
Hello sescobar,

I am running methane-air 1 step combustion, no particles, 30000 cells. My task manager showed fluent adding about .1GB every iteration until ram was full. Once ram was full the solver quit with an unable to malloc error.

So what I did was add 5 GB of virtual memory in windows 7 (it previously had no page file at all). Next time I ran the exact same case, the 32 GB filled up just like before, but then suddenly dropped to 3 GB while the solution kept going. It finished without incident 10 hours later.

I changed absolutely nothing inside ANSYS, so I have no idea why this happened. Apparently it does store each time step (how else could we explain going from a base 3GB to 30 GB while it was running), but as long as there is virtual memory it just dumps the ram when full. Strange.
ansys_matt is offline   Reply With Quote

Reply

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
Possible Bug in pimpleFoam (or createPatch) (or fluent3DMeshToFoam) cfdonline2mohsen OpenFOAM 3 October 21, 2013 09:28
How to start Fluent with Matlab?? Jay Hu FLUENT 5 October 9, 2013 14:20
Force can not converge colopolo CFX 13 October 4, 2011 22:03
define body force (rho* g) in fluent mohmed FLUENT 3 June 14, 2006 11:36
resume and run fluent for another timestep via a c greg FLUENT 2 June 30, 2005 05:01


All times are GMT -4. The time now is 07:35.