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.

"Constant" choice in Element Order for Discontinuous Lagrange Shape Function!

Posted May 25, 2023, 9:55 a.m. EDT Studies & Solvers, Equation-Based Modeling Version 6.0 3 Replies

Mahdi Nekahi
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi. I'm using COMSOL PDE to solve a set of partial differential equations that are linked together. In element order, there is a "constant" choice, but I don't know what that means! For example, I know what a "linear" element order means, but I don't know what a "constant" option means here. I get a better result with that choice! This "constant" choice only shows up in element order when the "Discontinuous Lagrange" shape function is chosen. So, what does that mean compared to "Linear," "Quadratic," and other choices? Thank you in advance for your help. Best, Mahdi

3 Replies Last Post May 25, 2023, 2:18 p.m. EDT
Henrik Sönnerlind COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 2 years ago May 25, 2023, 10:09 a.m. EDT

The value of the field described by this shape function is constant over each element. One effect is that it cannot be differentiated, since its gradient is zero.

-------------------
Henrik Sönnerlind
COMSOL
The value of the field described by this shape function is constant over each element. One effect is that it cannot be differentiated, since its gradient is zero.
Mahdi Nekahi
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 2 years ago May 25, 2023, 2:17 p.m. EDT
Updated: 2 years ago May 25, 2023, 2:25 p.m. EDT

Thank you.

Thank you.
Mahdi Nekahi
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 2 years ago May 25, 2023, 2:18 p.m. EDT

The value of the field described by this shape function is constant over each element. One effect is that it cannot be differentiated, since its gradient is zero.

Hi Henrik. Thanks for the explanation.

It is a surface evolution model, and z coordinate is the field to be solved with respect to time and (x,y) coordinates. After some run time, the geometry is still curved; it was initially an intact sphere and it is now a deformed sphere. How a smooth curved shape is possible using a constant shape function? Can you explain this more?

And, does constant shape function have the ability to capture the numerical solution accurately?

Thank you in advance for your help.

>The value of the field described by this shape function is constant over each element. One effect is that it cannot be differentiated, since its gradient is zero. Hi Henrik. Thanks for the explanation. It is a surface evolution model, and z coordinate is the field to be solved with respect to time and (x,y) coordinates. After some run time, the geometry is still curved; it was initially an intact sphere and it is now a deformed sphere. How a smooth curved shape is possible using a constant shape function? Can you explain this more? And, does constant shape function have the ability to capture the numerical solution accurately? Thank you in advance for your help.

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