Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Implicit Event leads to Singularity
Posted 2018年2月13日 GMT-5 07:12 General, Heat Transfer & Phase Change, Parameters, Variables, & Functions Version 5.2a 0 Replies
Please login with a confirmed email address before reporting spam
Hi All,
Issue: Satisfying an indicator state conditional on the time derivative of temperature leads to a singularity.
I am trying to implement an adiabatic boundary, by setting the heat transfer coefficient to 0, when two conditions are both satisfied under the events node. The conditions are 1) when the simulation time is in a specified time interval, governed by a periodic piece wise function that is either 0 or 1, when the function is greater than 0.9 then the first condition is satisfied; 2) when the temperature rate on the external boundary is greater than 0.02 degC/min.
When only the first condition is applied and satisfied, the simulation behaves as expected, the heat transfer confident is set to 0 by the variable “hOnOff” from the events node and the model goes into adiabatic mode. However when both conditions are applied and satisfied the simulation fails (Error: Repeated error test failures. May have reached a singularity. Time: 20917.62748343813. Last time step is not converged.).
As the simulation works under the first condition, I believe that no instability is caused from setting h=0.
Can anyone suggest why satisfy the time derivative of temperature (i.e. temp rate) will lead to failure of the simulation.
Many Thanks, Peter
Attachments:
Hello Peter B
Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.
If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.