Menu

Discussion Forum

New Discussion
Filter

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.

Irreversible temperature dependence process

Posted Jul 31, 2019, 8:43 a.m. EDT General, Modeling Tools & Definitions, Parameters, Variables, & Functions 1 Reply

Ofer Fogel
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,

I want to simulate irreversible thermal process same like phase change but in one direction. For the "phase change" I used alpha parameter which described by tanh (depends on T). however I want the process to be irreversible so when the matiral is heated the material properties will changed according to alpha but when the temp. goes down the materias parameter wouldn't change (not like alpha) How can I write this?

1 Reply Last Post Jul 31, 2019, 9:13 a.m. EDT
Jeff Hiller COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 5 years ago Jul 31, 2019, 9:13 a.m. EDT
Updated: 5 years ago Jul 31, 2019, 9:13 a.m. EDT

Hi Ofer,

If I understand what you're trying to accomplish properly, here's something you could do:

  • Add a distributed ODE to your model
  • Set it up so its dependent variable, let's call it "u", solves the equation du/dt=(T>Tcriterion), with the initial condition u(t=0)=0.
  • Having done that, you now have a variable that is equal to 0 unless the temperature has passed Tcriterion at any time in the past and takes a positive value if T has passed Tcriterion, and the boolean (u>eps) is equal to 1 if Tcriterion has been reached and to 0 otherwise and represents a state variable that you can use in your material properties to make them irreversible.

I am sure there is a more elegant solution, but the above should work.

Best,

Jeff

-------------------
Jeff Hiller
Hi Ofer, If I understand what you're trying to accomplish properly, here's something you could do: - Add a distributed ODE to your model - Set it up so its dependent variable, let's call it "u", solves the equation du/dt=(T>Tcriterion), with the initial condition u(t=0)=0. - Having done that, you now have a variable that is equal to 0 unless the temperature has passed Tcriterion at any time in the past and takes a positive value if T has passed Tcriterion, and the boolean (u>eps) is equal to 1 if Tcriterion has been reached and to 0 otherwise and represents a state variable that you can use in your material properties to make them irreversible. I am sure there is a more elegant solution, but the above should work. Best, Jeff

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content