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

Fluent running increadibly slow

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

Like Tree1Likes
  • 1 Post By MayTheFlowBeWithYou

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 10, 2017, 05:14
Post Fluent running increadibly slow
  #1
Member
 
MayTheFlowBeWithYou's Avatar
 
I have to remain anonymous, I'm sorry.
Join Date: Jun 2017
Location: The Netherlands, Delft University of Technology
Posts: 48
Rep Power: 7
MayTheFlowBeWithYou is on a distinguished road
Dear cfd-online community,

When I run serial simulations of fluent, sometimes the simulations will run very slow for no reason. The difference is quite extreme, a simulation that takes only 2 min to complete when it is running fast will take over 3 hours when it is running slow. And this is for literally the same simulation.

The only differences I have been able to notice between when fluent is slow and when fluent is fast are:
- when it is fast it does mostly not show the mesh.
- when it is slow, the cores are basically idle.

Clearly the last point is the key here, but I have no clue why fluent would not maximize its use of one of the cores. I even put the priority for all its processes on "realtime", this makes no difference.

The amount of other programs I have on also does not seem to influence it.

If anyone has any idea about what might cause fluent to run slower sometimes I would really like to hear it.

For extra information, I have these two screenshots of the taskmanager during times when fleunt is slow and when it is fast (both run the exact same simulation):

FAST:


SLOW:



P.S. Currently, I "fix" the problem by just restarting the pc until fluent runs fast. It's kind of like a game of CPU-roulette at this point.

Last edited by MayTheFlowBeWithYou; July 13, 2017 at 04:17.
MayTheFlowBeWithYou is offline   Reply With Quote

Old   November 3, 2017, 10:17
Default
  #2
New Member
 
Join Date: Oct 2017
Posts: 26
Rep Power: 7
Foxhunter is on a distinguished road
Do you use the parallel solver?
Foxhunter is offline   Reply With Quote

Old   November 3, 2017, 12:09
Default
  #3
Member
 
MayTheFlowBeWithYou's Avatar
 
I have to remain anonymous, I'm sorry.
Join Date: Jun 2017
Location: The Netherlands, Delft University of Technology
Posts: 48
Rep Power: 7
MayTheFlowBeWithYou is on a distinguished road
No, everything was in series.
__________________
MayTheFlowBeWithYou is offline   Reply With Quote

Old   November 6, 2017, 03:43
Default
  #4
New Member
 
Join Date: Oct 2017
Posts: 26
Rep Power: 7
Foxhunter is on a distinguished road
Quote:
Originally Posted by MayTheFlowBeWithYou View Post
No, everything was in series.
I am quite new to Fluent, but running the program in Parallel with the number of processes equal to the cores of my CPU kept the program running at 100% all the time. When I use series it sometimes goes a bit idle. Maybe it's something to fiddle with
Foxhunter is offline   Reply With Quote

Old   November 6, 2017, 15:09
Default
  #5
New Member
 
Bhanu Mahesh
Join Date: Jul 2017
Posts: 6
Rep Power: 7
bhanumahesh1993 is on a distinguished road
Do u use the same mesh size in both the cases or different?
bhanumahesh1993 is offline   Reply With Quote

Old   November 6, 2017, 17:40
Default
  #6
Member
 
MayTheFlowBeWithYou's Avatar
 
I have to remain anonymous, I'm sorry.
Join Date: Jun 2017
Location: The Netherlands, Delft University of Technology
Posts: 48
Rep Power: 7
MayTheFlowBeWithYou is on a distinguished road
Quote:
Originally Posted by Foxhunter View Post
I am quite new to Fluent, but running the program in Parallel with the number of processes equal to the cores of my CPU kept the program running at 100% all the time. When I use series it sometimes goes a bit idle. Maybe it's something to fiddle with
My simulation can't be run in parallel. This is also not the cause of the problem, the entire program is slower, including loading its own UI and stuff.
__________________
MayTheFlowBeWithYou is offline   Reply With Quote

Old   November 6, 2017, 17:41
Default
  #7
Member
 
MayTheFlowBeWithYou's Avatar
 
I have to remain anonymous, I'm sorry.
Join Date: Jun 2017
Location: The Netherlands, Delft University of Technology
Posts: 48
Rep Power: 7
MayTheFlowBeWithYou is on a distinguished road
Quote:
Originally Posted by bhanumahesh1993 View Post
Do u use the same mesh size in both the cases or different?
In both cases I run exactly the same simulation. With 'exactly', I literally mean exactly.
bhanumahesh1993 likes this.
__________________
MayTheFlowBeWithYou is offline   Reply With Quote

Old   November 6, 2017, 19:22
Default
  #8
New Member
 
Bhanu Mahesh
Join Date: Jul 2017
Posts: 6
Rep Power: 7
bhanumahesh1993 is on a distinguished road
Quote:
Originally Posted by MayTheFlowBeWithYou View Post
In both cases I run exactly the same simulation. With 'exactly', I literally mean exactly.
Generally speaking,
Laptops shows high performance in charging mode and low performance in battery mode. It's actually a system setting in many laptops. Do u observe the same case?
I mean, ansys run faster during charging!
bhanumahesh1993 is offline   Reply With Quote

Old   November 7, 2017, 07:34
Default
  #9
Member
 
MayTheFlowBeWithYou's Avatar
 
I have to remain anonymous, I'm sorry.
Join Date: Jun 2017
Location: The Netherlands, Delft University of Technology
Posts: 48
Rep Power: 7
MayTheFlowBeWithYou is on a distinguished road
Quote:
Originally Posted by bhanumahesh1993 View Post
Generally speaking,
Laptops shows high performance in charging mode and low performance in battery mode. It's actually a system setting in many laptops. Do u observe the same case?
I mean, ansys run faster during charging!
I am aware of this and I have set my laptop to use as much resources as it has while connected to a power outlet. In both cases the laptop was charging. The only thing between the two cases is restarting it. Where the "fast" case ran first, and the "slow" was after restarting. I ran these two simulations specifically for testing performance so all variables were kept the same as much as possible.
__________________
MayTheFlowBeWithYou is offline   Reply With Quote

Old   April 25, 2018, 16:02
Default
  #10
New Member
 
Francisco
Join Date: Apr 2018
Posts: 1
Rep Power: 0
Bigburd2323 is on a distinguished road
I have experience the exact same thing, it is very annoying. Did you ever find the source of the problem?
Bigburd2323 is offline   Reply With Quote

Old   April 26, 2018, 08:07
Default
  #11
Member
 
MayTheFlowBeWithYou's Avatar
 
I have to remain anonymous, I'm sorry.
Join Date: Jun 2017
Location: The Netherlands, Delft University of Technology
Posts: 48
Rep Power: 7
MayTheFlowBeWithYou is on a distinguished road
Unfortunately, I have never found the source. Currently, I don't do CFD work anymore so I don't think I will either.
__________________
MayTheFlowBeWithYou is offline   Reply With Quote

Old   April 26, 2018, 08:21
Default
  #12
Senior Member
 
Gert-Jan
Join Date: Oct 2012
Location: Europe
Posts: 1,659
Rep Power: 25
Gert-Jan will become famous soon enough
So the flow isn't with you anymore?
Then I hope you're in material science now, otherwise flows will be chasing you.
Gert-Jan is offline   Reply With Quote

Old   May 22, 2018, 03:04
Default
  #13
New Member
 
andrea robone
Join Date: May 2018
Posts: 1
Rep Power: 0
andreasydney is on a distinguished road
I have exaclty the same problem, someone can help me?it is very annoying and is impossible to work in this situation...i have already tried to install a second time Ansys but nothing change..one week ago was fast and now is incredibly slow and i can't work..not only run a simulation but even look at the graphics..i don't know what can i do..
andreasydney 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 overwriting of parameter values when Fluent is opened zubs FLUENT 0 April 10, 2015 06:18
[ansys fluent] problems of running ANSYS 12.1 fluent module mkwang2006 FLUENT 3 September 30, 2013 11:59
Hardware for running ANSYS Fluent 12.1 ngj_22 Hardware 2 September 29, 2010 08:26
PVM running of FLUENT Joe Yan FLUENT 0 February 27, 2006 04:48
FLUENT 5.2.3 running on PIII 733 Burley Wang FLUENT 7 April 19, 2000 07:03


All times are GMT -4. The time now is 00:31.