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Degree of Freedom

Posted 2022/05/17 10:03 GMT-4 Structural & Acoustics, Computational Fluid Dynamics (CFD), Structural Mechanics 3 Replies

Hitesh Kumar Sinha
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Hi, I am using 4 quadratic element in 2D square geometry for calculation of temperature. I get 9 values of temperature at each node using function mpheval, but when i use fuction mphmatrix to get K matrix it come 25x25. It says number of degree of freedom is 25.

How it is possible for scalar 2D Heat conduction problem? The K matrix should also be 9x9.

I am unable to find in document regarding degree of freedom. and internal degree of freedom Please help.

Hitesh Kumar Sinha Thank You

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3 Replies Last Post 2022/05/23 5:36 GMT-4
Henrik Sönnerlind COMSOL Employee

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Posted: 3 years ago 2022/05/18 7:01 GMT-4

If you look under Discretization in the Heat Transfer in Solids node, you will see that the shape functions used are Quadratic Lagrange, so there are 25 nodes in the mesh.

If you want to visualize the nodes, add a Mesh plot in any plot group, and select the physics interface in the Node points drop-down menu.

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Henrik Sönnerlind
COMSOL
If you look under *Discretization* in the *Heat Transfer in Solids* node, you will see that the shape functions used are *Quadratic Lagrange*, so there are 25 nodes in the mesh. If you want to visualize the nodes, add a *Mesh* plot in any plot group, and select the physics interface in the *Node points* drop-down menu.
Lars Gregersen COMSOL Employee

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Posted: 3 years ago 2022/05/23 4:35 GMT-4

Hi Hitesh

mpheval assumes first order elements by default.

If you set 'refine' to 2 then you'll get the second order information - and usually much larger matrices.

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Lars Gregersen
Comsol Denmark
Hi Hitesh mpheval assumes first order elements by default. If you set 'refine' to 2 then you'll get the second order information - and usually much larger matrices.
Hitesh Kumar Sinha
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Posted: 3 years ago 2022/05/23 5:36 GMT-4

Thank Henrik and Lars. Thank you so much for your reply. I helped me alot, thank once again for your guidence

Thank Henrik and Lars. Thank you so much for your reply. I helped me alot, thank once again for your guidence

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