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Active Member
benboubaker
Posts: 8
Registered: ‎04-21-2009

Steady Coupled fluid-thermal analysis with result temp vs time

236 Views, 4 Replies
01-15-2013 08:05 AM

i am trying to simulate  heat transfer of a chip on a PCB within a steady fluid.  but i would like to get the variation of temperature with repect of time. i have the chip enclosed in the box (air part included) and the chip, the box,  the air part and the board are enclosed  in a bigger enclosure with another air part included also.

i would like to get a plot result of themperature with respect of time.

Is Transient  Coupled fluid flow and thermal analysis is the right one to use, i am trying now and the Analysis progress continuous to run for more than 20 hours, is there a problem converging?

i have no problem with Steady coupled analysis for this model.

 

Regards,

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*Expert Elite*
AstroJohnPE
Posts: 521
Registered: ‎08-30-2012

Re: Steady Coupled fluid-thermal analysis with result temp vs time

01-15-2013 04:34 PM in reply to: benboubaker

Hello,

 

Transient coupled is required to get temperature versus time.

 

Steady coupled usually has a more difficult time of converging than transient because some (most?) situations do not have a steady state solution. Whether the transient analysis is having difficulty converging is a question that only you can answer: does the log file (the text that scrolls in the analysis window) show the percent completion increasing after a few iterations or after many iterations? (The online Help describes the text given in the log file: search for "coupled log".) Does the time step increase in the results environment?

 

The logs for the coupled analyses are tricky because there are three log files:

  • one for the coupling between fluid and thermal. This is the log file shown in the analysis window as the simulation is running.
  • one for the heat transfer analysis. This usually does not have anything of importance regarding convergence unless your simulation includes radiation, temperature dependent materials, or temperature dependent load. This log file is viewable from the "Report" environment.
  • one for the fluid analysis. This log file is viewable from the "Report" environment.
John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
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Active Member
benboubaker
Posts: 8
Registered: ‎04-21-2009

Re: Steady Coupled fluid-thermal analysis with result temp vs time

01-16-2013 07:33 AM in reply to: AstroJohnPE
when simulation runs, the first step of verifying the model is done, analysis progression bar move a bit, but there is no information showing in the window, the elapse time clock continuous with a blank window for 20 hours without any errors or any information in the window. usually the analysis will switch to result page during the analysis progression, no in my case.
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Distinguished Contributor
ilyas
Posts: 141
Registered: ‎06-13-2012

Re: Steady Coupled fluid-thermal analysis with result temp vs time

01-16-2013 07:28 PM in reply to: benboubaker

If I remember correctly, the last time I tried transient coupled fluid flow and thermal analysis, the graphic window does not update the results as the analysis was running. This made me a little bit confused and thought that my analysis setup was wrong. But when it was finished, the results for the all timesteps were accessible. Regardless, it was hard to determine whether the analysis is progressing or not. 

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Active Member
benboubaker
Posts: 8
Registered: ‎04-21-2009

Re: Steady Coupled fluid-thermal analysis with result temp vs time

01-17-2013 12:09 PM in reply to: ilyas
Thanks for the input, it seems the smpd.exe in MPICH2 was causing me a problem in Window7 (i am running as an administrator to avoid the problem), now i am able to see the actual analysis window with the regular info of updating velocity and temperature, but now i have a warning message 0X7A with an OK button that i am not able to click on to be able to continuous the analysis progression. i recreate the model about 3 times (meshing etc...) the same problem with the warning.
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