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-   -   Time periodic heating (http://www.cfd-online.com/Forums/ansys/106594-time-periodic-heating.html)

mfuchs September 3, 2012 05:11

Time periodic heating
 
Hi,

Im trying to modell the following 2d-system. There is a glas plate with a thickness of about 2mm and about 4 cm length. It is covered with a thin metall film (~ 10 microns). The film is periodocally heated from the upper side on one end of the system by a given heat current with an frequency of about 100 mHz. The heat sink is placed on the opposite end of the glas plate and is just a wall with constant temperature (293K)

http://www.abload.de/thumb/unbenanntz0bxr.png

The modelling and meshing is fine but it turns out that it takes very long to calculate and evaluate the experiment. The problem is that I have to use rather small timesteps (1/1000 sec) because of the evaluation that follows after the simulation. So here is the question:

Is it possible to get a time periodic solution? I have found something similar for ansys fluent:

https://www.sharcnet.ca/Software/Flu...ug/node392.htm

I do not need the start up phase but the start up phase lasts some hundred seconds. When I load the results in Ansys post it takes hours to get graphs.

thanks for your help
mfuchs

SaschaGH September 5, 2012 10:13

Hey mfuchs,

if I understand you correctly all you need to do is manually delete the unnecessary (.trn) of the start up process (check with your timestepsize) or a priori define in cfx-pre when the output of your transient results should begin, which can be done in the output control tab. With the reduced number of timesteps you can then create a transient chart in post to see whether your problem has time periodic character.

If your startup phase lasts some "hundred" seconds but you use 1/1000 sec, how many hours/days does it take to calculate the problem ? Ever thought of using a bigger timestep for the beginning to obtain transient stabilization faster and then switch to the desired timestep for evaluation ?
Greetings

mfuchs September 11, 2012 05:00

ok this works fine. Thank you.


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