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Parameter list gives empty sweep

June 9, 2014, 10:29 am
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Hello,
I am modeling a system intended to display light scattering off of a particle suspended in a liquid medium. I used Electromagnetic Waves, Frequency Domain (emw) and keep getting the error "The following feature has encountered a problem: Parameter list gives empty sweep - Feature: Parametric 1 (sol1/s1/p1).
What does this mean? Am I required to include a parametric sweep in order to use the pre-made study option? I only intend to model under one set of conditions.

Thanks,
Daniel Frantz
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increasing the speed of computation or parallel processing

August 19, 2014, 3:19 am
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Hi comsolers,

Is there any way to increase the speed of computation for comsol? now, my time series is for one month with daily resolution. and it takes at least 4 or 5 hours to compute. and I have more than 2 years data with daily resolution.
Is there any parallel process in comsol4.3?

Thanks for the help
Sepideh
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Abrupt change in concentration value

August 19, 2014, 4:02 am
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Hello,

I am attempting to model the evaporation of dilute species in an additive manufacturing process. For each added layer of material we have applied a boundary condition at the bottom, concentration C_0, and a boundary condition at the top, surface concentration C_s which is depleted of the dilute species.

We have a problem when adding additional layers due to these boundary conditions. For the first layer we have a concentration gradient from C_0 at the bottom to C_s at the top. However, when adding the next layer the top boundary of layer 1 (C_s) becomes the bottom boundary of layer 2 (C_0). The difference between these two concentration values is quite large.

What is the best way to approach this abrupt change in concentration at the interface between these two layers?

Thank you for any help,
Thom
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ERROR IN SIMULATION

August 19, 2014, 10:22 pm
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Hi

I am getting the following error:

"Failed to find a solution.
Maximum number of Newton iterations reached.
There was an error message from the linear solver.
The relative error (71) is greater than the relative tolerance.
Returned solution is not converged."

Can someone please tell me why I am getting this error and help me in this regard?
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optimising solution methods in parametric sweeps. newton step suddenly going wrong

August 20, 2014, 1:19 am
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I sometimes have my computations converging reasonably but then suddenly one step completely changes the picture and the error drastically increases, almost as if a calculation error had been made, probably something non-linear or a division by near-zero. See the images for an example of the convergence and how the solution step changes with a sudden peak in a small area of the domain.

Of course, I can solve this problem by changing the damping factor and the size of the mesh elements. However, when I am performing a sweep varying many parameters, these changes are an overkill. The problem with convergence only occurs in a few cases, for instance with very high velocities.

- Are there solutions to have the solution method adapt during a parametric sweep? I don't see these options but maybe some people have ways to tweak it.

- Also are there ways to have the solver realise earlier that it is going completely wrong? Like in the attached image I see clearly that it is wrong but the solver doesn't know yet, are there ways to forumulate this and let the solver work with it? I would be happy with all the rest of the parametric sweep and just have these problematic cases discarded. In my current case the solver gets stuck in these cases, taking much time to continue the calculation. With the result that after a weekend of computation I see my model is not finished because it got stuck in one particular case (I know of the option to continue if an error occurs but sometimes the solver takes a lot time before it realizes the error).
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Joule Heating

August 20, 2014, 1:48 am
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Hi,

I have started working with Comsol recently and I have been trying to create a model like this: four electrodes in a suspending medium (the model is based in salty water), on a glass surface.
The aim is to create a travelling wave signal so a sinusoidal signal with different phase is applied to each electrode.

I have tried to visualize the temperature after performing a frequency dependent study, but the temperature does not change. Any suggestion to this problem?

I'm trying to upload my model but I still didn't figure it out how to do it.

Thanks.
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Problem in convective flow simulation

August 20, 2014, 11:48 pm
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I am now trying to solve magnetophoresis model by coupling CFD and transport of dilute chemical species modules together. I want to study the dynamical behaviour of the process and I used Time-Dependent solver in my study. However, I found that 'Nonlinear solver did not converge' when I used finer mesh in my computation. Also, I found that it is more difficult to converge when I want to do the simulation for a longer time range.
The solver does converge when I used a coarser mesh and simulate for shorter time range. Yet, solver gives different solution for each computation (or study) and I think that the solution is not reliable due to the extremely coarse meshing.
I know this is a highly non-linear model as it involves convective flow (due to buoyancy force) and transport of chemical species. Is it possible to improve the convergence of the solver in order to solve this highly non-linear model by using a finer mesh? Thank you.

--
Leong
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can you help me?

August 21, 2014, 8:06 am
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Hi Yilong Zhou ,I want to simulate the mixing of nanoparticles. I have the same problem as yours. The simulation results are not consistent with the experimental results. Can you help me. Have you found the answer yet. Please advise me if you find answer your question. Thanks.
azabihi11@gmail.com
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Failed to find a solution. The relative error is greater than the relative tolerance.

August 22, 2014, 4:48 am
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Hi all,
I'm trying to simulate a Piezoelectric transformer using the piezoelectric devices physics.
My structure is quite simple:
it's a thin circular membrane of piezoelectric material thick 1um (AlN), with upper concentric electrodes for primary and secondary (inner circle is the primary while the secondary electrode sorrounds the primary electrode).
Under the AlN membrane there's silicon thick 4um
I run the eingenfrequency study step in order to find resonant frequencies, but when I run frequency domain study step, in a small range of the chosen resonance, I get the error: "Failed to find a solution. The relative error is greater than the relative tolerance".
As the problem has a cylindrical simmetry, this model is set in 2D-Axysimmetric

- I have to say that I get this error when the frequency is extremely close to the resonant frequency.
- I have inserted damping and losses for all materials, thus getting a finite quality factor (so the problem is not related to undamped response)
- I ve tried an extremely fine mesh
- I ve tried to change solver parameters (although i m not an expert in solvers) and this seems to change a little the frequency where I get the error (since the Q is around 4000, I've set a 100Hz frequency step), but at the end I always get the error.
- I ve read all forum discussions about this error, but nothing seems to help me.
- If I change the radius of the structure from about 500um to 50um, I do not get the error, furthermore the simulation is faster!

How can I resolve this error?

Thanks in advance!

Antonio
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frrofluid, magnetic field and diluted species

August 22, 2014, 11:01 am
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Hi, I want to simulate the concentration variation of nano-particle in a micro-fluid channel under magnetic field, I have built a modeling including transport of diluted species , laminar flow and magnetic field . I want to solve step1: stationary magnetic field and then step2: time dependent laminar flow and transport of diluted species. step1 solved good but I have an error in step2 .
Nonlinear solver did not converge.
Maximum number of Newton iterations reached.
There was an error message from the linear solver.
The relative residual (0.33) is greater than the relative tolerance.
Time : 0
Last time step is not converged.
Anyone got a solution?
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please help me?

August 23, 2014, 7:39 am
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Hi, I want to simulate the concentration variation of nano-particle in a Y micro-fluid channel under magnetic field, I have built a modeling including transport of diluted species , laminar flow and magnetic field . I want to solve step1: stationary laminar flow with two inlets: flow rate=[60cm^3/min]. step2: time dependent laminar flow and transport of diluted species and magnetic field by using initial variables from step1. step1 solved good but I have an error in step2 .
Nonlinear solver did not converge.
Maximum number of Newton iterations reached.
There was an error message from the linear solver.
The relative residual (0.33) is greater than the relative tolerance.
Time : 0
Last time step is not converged.
Anyone got a solution?
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Piezoelectric Transducers

August 25, 2014, 7:03 am
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Hi
I am analyzing the signals in piezoelectric transducers. Can somebody help me in finding some of the difficulties I am facing.

1) How could I measure electric potential of the container on which an piezoelectric is placed.

2) How could I calculate the vibrations being observed by the piezoelectric when one piezoelectric is used to emit the vibrations and other is used to receive the vibrations.

Kindly suggest me an answer to the above questions, which would be a great help to my project.
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Modeling ETD ferrite core

August 25, 2014, 7:18 am
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I am trying to model an ETD ferrite core (core losses) and i have been following the tutorial for an E core. (www.comsol.se/model/download/1...els.acdc.ecore_transformer.pdf)

However i experience a problem with the solver. Error message:

Nonlinear solver did not converge.
In segregated group 2:
Time : 0
Internal error in solver.
Last time step is not converged.

The file is attached. Any idea how to fix this?
Thank's very much in advance.

PS: I know i could make an approximation and simulate the core in 2d, but i want to compare with a more complex transformer, that needs 3d simulation
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Multiphysics

August 26, 2014, 6:37 am
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Hello.

I have such a question:

When I give the project the two physics that have the same output
for example, the magnetic field strength of the magnetic field
in T, and each physics shows intrinsic value.

what can I do to make these physics merged in the calculation
and gave one overall value?

Thank you.
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Definition of some parameters in Joule heating module

August 28, 2014, 5:35 pm
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Hi guys,
I am working on a simple geometry to simulate it with Joule heating module. While I am looking through equations in this module, I cann't find description of some of them. I appreciate if someone may help my about them:
1- Under Joule heating model for domains, what is Q_j (and its difference with Q) and J_e and also epsilon_0?
2- Under boundary electromagnetic heat source, what is Q_sh and since we have another boundary condition for electric field such as electric insulation, why we need boundary electromagnetic heat source?
I am sorry if the question looks awkward, but I really need to know what is going on within the fundamental equations of simulation.
Thanks a lot.
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Request for your help

August 30, 2014, 6:01 pm
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Dear Ivar,
Hope everything goes well with you. I have posted a thread in the forum, but till now no reply. Since the question is important for me, I would appreciate if you would look through the it and see whether you have any idea about it or no. the thread is: www.comsol.com/community/forums/general/thread/47053/

I highly appreciate any kinda help from you. Really don't know better expert than YOU!
Regards,
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Question about Comsol

August 31, 2014, 5:26 am
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Good day.
 
1 If I have more physics in the model together so do not cooperate and give me different results for the same quantity.
2,If I have the model used by electric or magnetic object eg. coil field lines are not all visible.
  And if I put in a magnetic or electric field somehow metal or insulator, there are no more moves.
3.Missing there simulation of gas ionization by an electric field or temperature.
 
Thank you very much for your willingness.
 
Goodbye.
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COMSOL in parallel mode: a speedup of 20% using 4 cores?

September 23, 2009, 1:01 am
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Hello everyone,

I have performed the following experiment. Using the command -np #cores, I have forced COMSOL Multiphysics to use 1, 2, 4 or 8 of the available cores on my computer. I also used the default configuration of COMSOL Multiphysics, i.e, without the command -np. I performed the experiment using two models comprising two drift-diffusion equations coupled with the Poisson equation - one is quasi-linear, the other is highly non-linear. The solver used was Pardiso. The results are in the attached file.

I have obtained a speed-up of about 20% when I activated 4 cores, as compared with the duration of calculations using only 1 core. Do you believe that this improvement of 20% is the typical speedup that can be obtained? Does anyone have some more data or experience on this issue?

Thank you for your help.

Kind regards,
Pedro
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inductive heating - moving mesh problem

September 1, 2014, 6:14 am
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Hi,

i try to simulate a 3D model with a rigid coil over a moving metal-part. The simulation consists of three physics: moving mesh (ale), magnetic and electric fields (mef) and heat transfer (ht).
I implemented all three studies and particularly they work fine, but the problem is that the electromagnetic heat source moves with the partboundary and does not remain under the coil.

I have three single studies:

1. time-dependent: ale
2. time-dependent: mef
3. time-dependent: ht

So can anybody tell me where is my mistake?

Thank you

Robert
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Failed to find consistent initial value

December 20, 2011, 3:49 am
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Hi, everyone,

I try to build a model based on the “Heat Transfer” module and the “ALE” module, just as the .mph attachment shown. When solving it, the following error occurs (just shown in the .png attachment).

”Failed to find consistent initial values.
Undefined value found.
NaN or Inf found when solving linear system using PARDISO.
Last time step is not converged.
-Feature: Time-Dependent Solver 1 (sol1/t1)
-Error: Failed to find consistent initial values.”

What is the reason and mistake? Would you mind giving me some suggest and help?
Thanks sincerely in advance for your help.
Best wishes to you and your family.

Yours
FM Huang
Dec.20th.2011
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