Hex and Tet meshing in thermal anlaysis

[xuxxx679]

Hi,

I've been told that hex meshing is always better than tet in mechanical simulations (stress, contact, etc). I'm wondering if the same thing is true in thermal analysis? Also, is it required to use hex20 instead of hex8 for transient thermal analysis since for transient the heat equation is second order? I'd really appreciate it if someone can share his/her thoughts with me on this.

Thanks,
Danny

 

[whitwas]

Hex elements aren't necessarily better. If they take more time to generate the mesh, that can offset the time saving they provide in the solver, but typically, yes.

The "second order" has two different meanings here - for the elements it means temperature is a quadratic function of position and for the heat equation it means it has second derivatives of temperature. Second order elements aren't required for transient thermal analysis. If you use them, you can get a piece-wise quadratic temperature gradient instead of piece-wise linear that you would get with linear elements, so you may need fewer pieces (elements). In the end, both are approximations, especially if the actual temperature function is exponential.