Time step size - Thermal Transient Analysis

[kirandabhade]

What is typical time step size used in thermal transient analysis? 0.01 s and 1.0 s yield to different stabilized temperatures with different heating rates.

[apolo_vanderberg]

This depends on what is going on in the system.

Is this a transient flow + thermal? or conduction only?

Depending on the amount of heat entering and how some materials may change their properties, this can impact the timestep size used.

As an aside when you state they yield different stabilized results:

• What results did you get for each?
• How different are they?
• Did you run out to the same physical time for each?
• Was solution control turned on or off?
• What advection scheme did you use?

[kirandabhade]

we are doing only for Themal Transient  analysis not for flow .

For your first 3 question i have attached one graph from that you will get idea about result and effect of ISC by keeping enable and disable.

For this analysis we are using advection scheme 5

[apolo_vanderberg]

With ISC enabled, you are allowing the solver to adjust the timestep such that with a given timestep prescribed Solution Control can alter this value as needed . So 1000 steps of 1sec prescribed may not actually be 1000sec, but could be less.

From the graphs you posted it does appear that 1sec and 0.01sec (both ISC on and off) seem to be following the same trend. Obviously you will need to run the 0.01sec forms out further to see how it trends across the full 1000sec but they do follow the same path.

It is a bit odd that the 0.1sec (as it had ISC on) did not follow the same path. It's tough to say specifically what cuased that one run to divert from the path that the other 3 were showing.

[kirandabhade]

As per your suggestion I have already run that case for 1000 Sec for 0.01 sec time step size but it show me analysis completed successfully at different rate in time and stabilized temperature.

if you look at graph for 0.01 Sec with ISC enable it stopped at 95 sec and when it was disable then it stopped at 236 Sec.

My interest is to find out the rate that temperature increase in time with stabilized temperatures from that graph it show me always different rate in time and stabilized temperature

can you tell why it happened and way to find out rate that temperature increase in time and stabilized temperature.

[Royce_adsk]

Hello,

Could you share your support share file so that we could investigate?

Thanks,
Royce