Elmer Discussion Forum

Here the keywords "Quadratic Approximation" and "Use Piola Transform" relate to the 3-D solvers where the discretization is done in terms of curl-conforming (edge element) basis functions. The 2-D version uses standard basis functions and doesn't need these commands. However it m...

Some comments on the BC named as "symmetry": - to obtain symmetry the normal component of the velocity should be set to be zero, together with the do-nothing (default) BC for the temperature - if a component of velocity is specified, the corresponding component of the surface traction cann...

Suitable BCs are explained in Section 13.2.2 of the documentation https://www.nic.funet.fi/pub/sci/physics/elmer/doc/ElmerModelsManual.pdf as "For example, outgoing waves may be approximated by setting Z = −rho_0 c and ZT = −iω/c on the outflow boundary". That is, one has to give also an im...

Thanks, your changes have now been merged. I noticed a small mistake in a size specification of memory allocation. It is also fixed in the devel branch.

-- Mika

Hi,

I think you have done right code modifications to allow for a normal-tangential BC with UMAT. They might well be worth creating a pull request.

-- Mika

I made a small change to the devel branch so that mass-proportional damping (Rayleigh Damping Alpha) for translational motions can now be given for the beam solver, whereas giving Rayleigh Damping Beta = ... causes a warning message.

The beam solver doesn't yet understand the Rayleigh damping parameters, but adding the Rayleigh damping would be an easy modification

Both these cases are free vibrations and were supposed to vibrate forever with a magnitude of the initial displacement as there was no damping First, it might be good to mention that while this is expected for an analytic solution, computational time integration methods often have numerical damping...

As another test, I now checked that if the initial deflection is such that the displacement component U 2 depends linearly on the coordinate X in the absense of external loads, U 2 at the free end starts to oscillate like this end-u2.png Probably a refined mesh would be needed, so that all eigenmode...

There seems to be a problem that the beam solver has not automatically set the order of time derivatives. Therefore one has needed an explicit command Time Derivative Order = 2 in the sif file. I however updated the code as https://github.com/ElmerCSC/elmerfem/commit/7fe6d9b916d272db36f02019b202aa2c...