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Failed to find consistent initial values.

January 10, 2012, 2:11 am
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Hi.

I coose frekvenci transient study and get thise error.

Failed to find consistent initial values.
Last time step is not converged.

THANK
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Condition for remeshing could not be evaluated !!

August 4, 2017, 2:35 am
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Dear All COMSELer's ;

I am trying to model a moving mesh problem, where an object is moving by a 5[m/s] velocity a way from another object. i used the sliding mesh Technic , where i created 2 unions and performed an assembly between them so i can get Identity boundary pair so the moving part can slide over it .
Now, the deformed mesh is relatively large 90[mm] which require adding Automatic remeshing , but as i add a condition i got this Error ;

The following feature has encountered a problem:
- Feature: Automatic Remeshing (sol1/t1/arDef)
Condition for remeshing could not be evaluated.

My remeshing condition is ;

sqrt(comp1.spatial.I1isoMax)>2

same as default , which is really weird !!
Any help ?!
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Fluid Structure Interaction with Piezoelectric

September 3, 2017, 10:41 pm
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How to couple the fluid structure interaction with piezoelectric device? A tube is squeezed by a poezielectric device. And the tube affects the fuild in the tube.
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CFD , SST

September 4, 2017, 2:25 am
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Hi,

I am using the SST turbulence model to simulate a thin film flow between to rotating cylinders. I am able to get a converged solution up to a certain mesh size, but as soon as I add another element in the thickness direction of the film I can no longer get convergence.

Could this be because Comsol abandons the wall functions at this stage because the mesh is considered fine enough and then the mesh is all of a sudden too coarse to integrate the flow all the way to the wall?

Also, in the manual where the SST model is described there is a parameter called lplus_cc but all I can find in Comsol is lplus_w, are they in fact the same variables?

Best regards Philip
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Suggestion needed for making 2d animation video.

September 4, 2017, 4:34 am
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Hello,

I am working on a freelance project designing and creating a production companies end logo that will bookend all their cable shows that will air on such cable stations as TLC/Discovery to mention a few. I'm not sure what kind of money I should charge. It will include 3D logo design and 2d App Intro integrated into After Effects for final compositing using camera and object motion tracking from C4D to match 3D layers in After Effects. Please help me with your suggestions.

Any suggestions would be much appreciated.

Thank you.
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Splice

September 4, 2017, 6:56 am
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I would want to splice two optical fibers using the filament splicer splicer. Prior to it i would want to model it in COMSOL to know the temperature distribution along the axis of the fiber when changes are made to filament parameters like the power, splice time ... Is there a model in COMSOL that can be used for this? The filament i'm using for the splicing is omega shaped.
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Plasma simulation, initial conditions of species

September 4, 2017, 7:10 am
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Hi all,

I am modeling some plasma chemistry and having gathered all the reactions of interest which include neutrals, excited states, ions etc I managed to run my simulation without any problems. However, I am interested to know how the initial conditions of my problem are calculated. I see in the log window that the log of mass fraction of my ionic species and excited states are higher than the neutral species even though I gave higher initial values to these species. I see this difference in species of comparable masses and this is what made me wondering. I am going through the manual and the applications library of course but if you can contribute somehow that would help a lot.

Thank you, Leo
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Heating steel in an oven

September 4, 2017, 7:18 am
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Hi,

I'm trying to make an, in my mind, easy model. The idea is to heat up steal in an oven of +/- 1000K.
I'm using heat transfer in solids for the metal of course, but I can't figure out how to model the air in the oven and to make clear that the heat must be transfered in the metal.

I've tried heat transfer in liquids but I can't get it working properly.

Hopefully someone knows the solution :)
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CFD & Heat transfer analysis of disc brake. Multiphysics Simulaton, Conjugate heat transfer with turbulent flow

September 4, 2017, 8:43 am
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Hey Everyone,

I am trying to simulate CFD of disc brake to understand the airflow and how it affects the cooling of the disc brake. I am using Conjugate heat transfer module with turbulent flow. I made a basic geometry of disc and hub.

I am attaching the model below.

Thanks in advance for any suggestions or help.

Abdul Haq
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Material properties on a boundary

August 15, 2011, 12:08 am
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Hi everyone,

I am using the physics builder interface make my own heat transfer mode and would like to include the emissivity for radiative heat loss. Everything works fine with my heat balance correctly accessing my materials (also with customized material groups) on the selected *domain*, except for the emissivity. The solver returns an error that it cannot find the parameter and, if I look at the materials node, I see that boundaries 1-4 require a material (despite the fact that the domain enclosed by these boundaries does have the material.

I saw a previous thread where Ivar commented:
" As by default in COMSOL the boundaries do NOT heritage the domain material properties, particularly because in "union" mode, you have a common boundary for two adjacent domains, so COMSOL cannot choose by itself which of the two materials to set on the common boundary between the two materials.
"

This makes sense to me (nicely pointed out!), but I wonder if there is an alternative to the default which may be enabled? There are a number of workarounds (the simplest of which being including the material again, this time on the boundaries) but it strikes me as sloppy.

Anyone have any suggestions?

Thanks!
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how to synthesize a OAM light in COMSOL

November 3, 2016, 8:45 pm
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Hi,everyone:
I have designed a circular photonic crystal fibe,and i can get the the effective refractive indices of the fiber eigenmodes,but i want to analyze the OAM light through its intensity distribution.however, the OAM light synthetic formula is ( even mode ± j ⋅odd mode ),how can i do to get the The superposition of eigenmodes.
pleale give me some suggestions.
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How to calculate potential difference between two triboelectric surfaces

June 14, 2017, 4:07 am
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Hello everyone,

I want to find the potential difference between two triboelectric surfaces (PDMS & AL) arranged vertically. Aluminum is used as an electrode and triboelectric surface.

I want to use this equation V = σ x(t) /ε0

V=potential difference, σ= surface charge density (1 μC/m2) , x(t)= distance between the surfaces, ε permitivity.

I want to vary the gap distance between the surfaces and check their effect on potential difference.
I want the result like shown in the attached image
Thanks in advance
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Boundary Conditions Solid Mechanics

September 4, 2017, 6:04 pm
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Hello everyone.

I'm trying to simulate a multilayered assembly of 4 different materials subjected to a temperature gradient. I want to use Comsol to validate a numerical method that I've been developing. When the interface between two adjacent layers is flat, the simulation reproduces the behavior of my code. Nevertheless, when I put boundaries that are not flat, there're differences between my code and the simulation that COMSOL provides. I want to know if it is possible to know the exact boundary condition that COMSOL is setting at the solid-solid interface (the balance equation), in order to see if I am doing something wrong or if there's an additional term that COMSOL is considering that I am not.

Thanks in advance.

Daniel A.
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Center line velocity of curved 3D pipe visualized in 1D line graph

September 4, 2017, 11:09 pm
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Hello all,

I want to plot the center line velocity of a curved 3D pipe over the arc length which has several curvatures with different angles.

In the application library the example "Flow Through a Pipe Elbow" (www.comsol.de/model/flow-through-a-pipe-elbow-12221) exist.

Taking this example, how could I plot the center line velocity over the arc length? I want to compare the results with a 2D axis symmetric solution. In this case it is simple, just taking the axis of symmetry as data set and plot it.

Best regards

Andreas
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particle tracing in nonuniform magnetic field

September 4, 2017, 11:26 pm
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Hi. how can i simulate the trajectory of the charge in non stationary magnetic field and electrostatic field ?
is there any one who can help me?
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How to find value of a function at a point with high accuraсy?

September 4, 2017, 11:37 pm
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Dear colleagues!
I have a problem. It's need to me to calculate value of function f(x) in some point x = x0, i.e. to calculate f(x0), where f(x) is 1D plot. One time again:
1. In "results" there is plot of function f(x).
2. I should find value of function f(x0), where x0 - some point.
3. It's need to me to write value = f(x0) in some field in Application builder.
How I can to do it?
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Joule heating using terminal

September 4, 2017, 11:52 pm
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Hello.
I'm trying to simulate the process of plasma-plasma sintering.
To set the heating rate, I model the PID controller with the input current at the upper boundary using the terminal.
But the resultant current at all points of the model is the same, which is incorrect.
What's my mistake?

I added a link to the model file, because I can not attach a file here.

yadi.sk/d/_DdnVw1t3McJo7
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Changing the sampling rate of variables

September 5, 2017, 12:31 am
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Hi everyone,

i want to implemate a real PID-algorithm in comsol. I use global equations to realize this. In the real controller the sampling rate is 0,1s.
That`s why i want to change the sampling rate of calculating the variables to 100ms. (and not in every iteration step)

Can anyone tell me how i can change this?

Or is there a opportunity to change the time in which the measuring probe are queried?

Thanks in advance.
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Solid inside a droplet

September 5, 2017, 1:37 am
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Dear All,

I want to model a solid object inside a droplet. I want to move the solid object along with the droplet. How can I combine solid mechanics with laminar two phase flow. Is there any other option to specify prescribed displacement or velocity for solid object computed from laminar two phase flow.

Regards,
Ismail
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Applying CFD

September 5, 2017, 7:01 am
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I am trying to add CFD into heat transfer model for welding such that during welding when metal is in liquid state it will have some convective velocity but when I am trying to do so I am getting an error message stating that .I am attaching screenshot of error message can anyone help me with this issue.
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