Discussion Forum

Hi

I do not know all the parameters from the solver, but what you see is that the solver made a large step, then was not happy with the convergence, and reduced the step, tried again, failed, then reduced it again. This is typical for iterative solvers, I'm not sure how much of the results of the larger steps are used for defining next smaller step, but the last valid steps are at least used to project to the next solver step.

This is the typical behaviour of the iterative solver, in "free" mode.

You can also force it to do only your defined steps, but then there is a fair chance that it will just stop when it discovers that it is diverging. check the lower level solver sub-nodes

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Good luck
Ivar

Hi again,

I am once again trying to understand the information that is given to me in the Log tab.

my log is here, every space was replaced with _ so that it will be readable. (sorry for the long wall of text)


Step________Time____Stepsize______Res__Jac__Sol_Order_Tfail_NLfail_LinIt___LinErr___LinRes
___0___________0_____________out____4____6____4__________________0
___________________Group_#1:________2____3____2_______________________14___0.0091__0.00022
___________________Group_#2:________2____3____2________________________4__0.00037__1.9e-06
___1____0.031416____0.031416________6____8____6_____1_____0______0
___________________Group_#1:________3____4____3_______________________21___0.0086__0.00056
___________________Group_#2:________3____4____3________________________6___0.0039__3.3e-06
___2____0.062832____0.031416________8____8____8_____1_____0______0
___________________Group_#1:________4____4____4_______________________32___0.0098__0.00045
___________________Group_#2:________4____4____4________________________9___0.0011__7.2e-07
___3_____0.12566____0.062832_______10____8___10_____2_____0______0
___________________Group_#1:________5____4____5_______________________42___0.0073__0.00037
___________________Group_#2:________5____4____5_______________________11___0.0087__8.8e-06
___4_____0.25133_____0.12566_______12___10___12_____2_____0______0
___________________Group_#1:________6____5____6_______________________51___0.0063__0.00019
___________________Group_#2:________6____5____6_______________________14___0.0015__1.3e-06
___5_____0.50265_____0.25133_______16___12___16_____2_____0______0
___________________Group_#1:________8____6____8_______________________58___0.0056__1.1e-06
___________________Group_#2:________8____6____8_______________________18__7.8e-09__1.8e-11

...


from what I understand, the step is clearly the step number; time is the current value of the t variable; stepsize is the stepsize of the time jumps in every step. these are the easy ones of course. my question is about the next ones, if anyone can help me.

in the step size column there are always the group #1 and 2, which to my understanding, gives me the information for the each group in the segregated solver.

about the Res, Jac, Sol, I don't understand it at all; the Sol and Res columns are exactly the same, so I suppose that the res is some result of a computation and that the sol is the final value, which happens to be the same. I don't know what the Jac means(I'm guessing it's jacobian somewhere but I don't know where/how it is relevant).

then there are the Order, Tfail and NLfail. what do they mean?
likewise about the LinIt, LinRes, and LinErr. I guess that the 'It' refers to iteration, Res is result and Err is clearly error - but what is that Lin which is talked about?

I want to be able to understand the log and conclude about how the computation is progressing - please help :(

it should be noted that the solver is the default for Induction Heating in a Time Dependent model.


Thank you very much for your time,
Shoval

Hi

welcome to the club ;)

Well I would also be interested to better understand some of those.

one you missed is the "out" that indicates that COMSOL has interpolated for a user requested time (or parameter) step and saved the related solution data set part

By the way there is a way to get the solver to tell even more (not much but info on scaling etc) check the solver sub nodes "logfile: detailed

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Good luck
Ivar

ahh yes, the out is something that I figured as well, it appears more in the next parts of the log and exactly at time=pi/4 *n, which is the times I asked for the interpolation, so I understood this :)

is there some dynamic help about this, or anything in the tutorial?

The log file variables are explained in the documentation. See COMSOL Multiphysics > Solvers and Study Types > Solver Studies and Study Types. I only found this documentation section recently, so either they added it recently or I was just looking in the wrong place.

Nagi Elabbasi
Veryst Engineering

Hi, Happy New Year,
and thanks for the link Nagi

I found more (or the same) in the help under search "Progress and Log Information"

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Good luck
Ivar

Hi again,

firstly I would like to thank you for the information you provided above, it proved helpful :)

second, I have a new question related to this subject. Once again I will post a partial quote of the log:

Warning: Inverted mesh element near coordinate(0.4,-0.478926,-1.57896).

This line appears around 50 times in my log file now; it appears almost after every line, multiple times. Why does it report so much about the same thing? do you know what it means?

The computation is running for almost 80 hours now, so I am not stopping it; but it seems wierd - especially since my model is very small, and the Z coordinate -1.57 is far away from the place where the physics matters. what I'm trying to say is that my model is around 1mX70cm on area and around 12 cm on height(Z coordinate), and around it there's a sphere of air in radius of 2m, so what's wrong with that specific coordinate?


Thank you very much once again for your answers and time,
Shoval

You have a bad element at the specified location which would put it in the air region. The solver does not keep track, it seems, of the mesh warnings that it reported in previous calls so it will give you this message more than you care to see it.

Nagi Elabbasi
Veryst Engineering