Discussion Forum

Hi

for me it looks like you are missing some material properties, or that your mesh is not full (some domains are not meshed), difficult to say more just from such a message I agree ;)

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Good luck
Ivar

Hi Ivar,

Thank you very much for your reply. I guess you have a sound understanding about COMSOl


I have been facing another issue while i was working with COMSOL.(4.3)

The problem is like ....for a particular mesh size I can not simulate below a certain frequency.
If i increase the mesh size then i can do it, i want to simulate my structure below that certain frequency without increasing the mesh size .

The error message I get is "

Failed to find a solution for the initial parameter. The relative error (0.0013) is greater
than the relative tolerance. Returned solution is not converged. :"

Could you please give me any suggestion . IF you need any further info, plz let me know

Thank you
Sanjay

Hi

first of all, COMSOL might find a solution with a coarse mesh, but it can be all wrong, if your mesh is too coarse. You need to have a mesh size that is sufficiently dense to catch the gradients of your dependent variables, and in case of waves that you have at least 5 or more mesh elements per period, in the material. Else you are under sampling and your results will be wrong (even if COMSOL sometimes might converge.

It's like aliasing in sound digital recording, a pure numerical sampling theory effect.

What is tricky is that often the gradient opf the dependent variables are very steep for given initial conditions, so often you need very fine mesh only very locally, and in time dependent , often only for the fist steps (typically for diffusion from a step concentration or thermal boundary limit. Then its worth to cheat a bit and introduce a >0 concentration or temperature locally close to the boundary with the initial conditions, it helps for the convergence. Often this is more critical for concentrations than for T as T is offset by 273°K most of the time, while the concentration is =0 as default initial value, and any c<0 makes people and COMSOL to scream ;)

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Good luck
Ivar

Hello Ivar,

I am new to COMSOL and had the same error, "variable property doesnot include all variable in Xmesh" while performing my simulation. I am attaching my COMSOL file for you understand in detail.

Best Regards,

Nishtha

Hi,
I have a same convergence error with a finer mesh or a lower frequency. I start to think some comsol solver
may use single precision even within the 64bit version. But I am not sure about that, because I haven't found any option about this precision in solver. Have you solved this problem? If do, please let me know.
Thanks!

Hello everybody,
did you solve the xmesh issue?

I got the very same error "message":
"Variables property does not include all variables in Xmesh"

I imported a coil geometry from solidworks via livelink. My aim is to simulate the distribution of magnetic flux density around the coil as a stationary problem (mf). I added the grounding and side feed boundary according to the 3D inductor tutorial privded by comsol.

I very much appreciate any hint/help,
Best,
Sebastian

Has anyone figured out what this error is caused by? I verified I am not missing any materials. I can get my model to solve if I just use extra-fine tetrahedrals, but it requires ~300K elements and takes more than a day to resolve. I used some mapped meshing and triangles to get the elements down to ~17K, but I keep getting this error whenever I try to solve. The triangle meshing has a Geometric entry level of Remaining, so I assume everything is meshed (otherwise, what is the point of this setting?). Can someone please provide some insight into what could be causing this error.

Thank you,
Ian