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mesh quality not achieved

February 14, 2013, 9:15 pm
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I am trying to simulate a problem where the particle is moving in the domain. So i have used moving mesh (ale) and assigned a value to prescribe mesh velocity for the particle's boundary. The particle has been considered as moving wall and it moves at the same velocity as the mesh. I have also decreased the minimal mesh quality to 0.001, but still it is giving the error " Requested mesh quality could not be achieved".

Can someone suggest to fix this error ??

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Pressure boundary conditions

February 14, 2013, 11:02 pm
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Hi All,

I am working on a coupled problem involving a piezoelectric and fluid.....I need to apply the pressure from the piezoelectric after each iteration step and apply it as a pressure boundary condition on the fluid.

Can anyone give me some ways to solve this problem.

Regards.
Rahul Kishor
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error:1038 File created by a later version of COMSOL

February 14, 2013, 11:15 pm
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Hi
I work with version 3.5a.
I want to open a file but i encourage an error:1038
File created by a later version of COMSOL

How can i open it, i think it is with version 3.5

Thanks in advance
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PCF with Matlab live link

February 14, 2013, 11:18 pm
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Now i am designing on hexagonal structure PCF of six air-hole rings and successfully
interface comsol 4.2 with matlab live link. The problem is that it takes a lots of time to simulate in Matlab when simulation is done in matlab.
Is there any procedure to reduce the time.



Thanks in advance.
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Simulating a Magneto-caloric effect in Comsol

February 15, 2013, 1:22 am
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I have a problem in which i have a permanent magnet. In regards to theory of Magneto-caloric effect, if i pass the magnetic field to the gadolinium(rare earth, lanthanide group in periodic table), there will be an increase of temperature(in Gd) due to magneto-caloric effect and when i remove the magnetic field from the Gadolinium, the temperature decreases and drop below the room temperature. My questions are:
1) I can able to create a block of Gd using the Gd's physical property but how to create a block of permanent magnet in Comsol?
2) Do i need to use a step/ramp function when i want to increase or decrease the temperature in the Gd, due to MCE?

Please advise and thanks in advance.
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phononic crystal -- Acoustic Structure Interaction

February 16, 2011, 2:28 am
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hello,

i'm computing the phononic crystal band structure using the Acoustic Structure Interaction modal, and the PC is 2D
square lattice and the unit cell is a circle in a square area. the problem is that when the square is liquid and circle area is solid, the band structure is good. but when the square is solid and circle area is liquid , that's to say, the liquid cylinder in the solid base, the computing result is worse, besides the wanted band , there are many flat bands , which are like the locally resonant mode ,
i'm troubled with it.
can anyone help me solve this problem, and give me a way to remove these flat bands

thanks!!!!
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Heat Transfer in Soils

November 28, 2012, 9:55 am
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Hi,
I am a comsol user and I want to have a 2d axisymmetric model. In my model, I have a soil sample that I put a steel bar in the soil. I want to heat the steel bar with a constant temperature 500(k) and then wait for 6 hours to see that how the heat will be conducted in the soil. The problem that I have is that after simulation, I do not know why I could not have good results. The heat will just be conducted at the top of the model, and the rest of the model will remain unaffected. You can see my model in attached file.So if it possible, I want to know that what do I need to do to solve this problem? Where is my mistake?

Regards,
Al
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Mie scattering in 4.3

January 7, 2013, 4:44 am
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Hello,
I have already seen some discussion about mid scattering of a gold nanosphere. But I the discussions I have consulted, no one has yet implemented a mie scattering program in Comsol 4.2 or 4.3 that works as the one in 3.5. Has this problem been solved yet? Can anyone post the correct program here?
Thank you very much for the help
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Using the Optimization Module for geometry examination

February 5, 2013, 2:31 pm
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Geometry optiization 4.3a
Simple 1D sold state battery problem (in COMSOL)

Done with assistance from COMSOL
M = length of anode 320 nm
L = length of solid electrolyte 1500 nm

objective function = external voltage
time to 2000 sec (time dependent)

If L & M are listed with the mins and the max, no problem.

However if they are coupled - L+M= 1820 nm there seems to be no way to include this in the optimization module.

Does anyone any any ideas?

Thanks

--
Arthur Rupel
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Preparation of figures for papers/thesis?

February 10, 2013, 8:19 pm
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If it has been written somewhere, can someone point me to where there is a guide to producing figures from 2D plots?

I am using COMSOL 4.2a, and want to use some surface plots alongside legends of the colour tables used. It is bizarre that COMSOL does not provide vector graphics export. I have tried to generate a decent image using the png export (via the 'snapshot' button -- is there any other way?), but it is horrible.

How I am doing it is:
1. Use highest 'Quality' settings in each component of the plot group that has such a setting (e.g. Surface; Contour)
2. Set export resolution to 1200 DPI
3. Set image dimensions to highest possible (for me it seems 4096 pixels is the upper limit?).
4. First generate a snapshot without any includes (i.e. no title, legend, axes. etc)
5. Then generate a snapshot with the legend included.
6. In GIMP cut and paste and scale as required.

See attached file for example of trying to export a surface plot with two colour legends. The model image part of the figure is tiny, and the legends huge.

If anyone has any tips or a separate set of routines in python/matplotlib or similar already in place I would love to see it!
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Integration of MATLAB functions with more than one variable

February 15, 2013, 4:43 am
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Hi,
I want to realize an integration in COMSOL 4.3a using self-written MATLAB functions.

If I use a test function with one input and one output argument everything works as expected (plotting function, integration).
If I now use a function with two arguments I still can plot the function with respect to x and y, but I will get an error when trying to do an integration:
"Evalutation of result expression - Unknown function or operator."

As I said I can plot the function correctly, so it can be found. And on the other hand functions are also found in integration when using a function with one argument.

Any ideas what could be wrong and what the solution could be?

Best,
Erik
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Inductively coupled plasma-High vacuum-Laminar flow-Free Molecular Flow-times range in Frequency Transient

February 15, 2013, 8:39 am
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hello!
*** first question: I try to simulate the device using the PLASMA MODULE (inductively coupled plasma) and LAMINAR FLOW in a vacuum (10 millitorr). The problem is that when I run the solver, had very long time solver works! my time range of Frequency-Transient solver is (1e-8) to (1e-3). I look at the log and convergence plot, the process starts from the time (1e-013) and up to the about (1e-7) the process goes quickly, but then stays on for a long time at this time and several hours process work without promotion. wanted to know what could be the problem?
*** second question: how can simulate a high vacuum but with laminar flow? the point is that device are in a high vacuum (1e-5 torr) and enters into device argon gas (0.1mg/s) and by a high frequency, plasma is formed. The problem is that when I use the laminar flow, this module does not respond less than (10 millitorr) and when I use the Free Molecular Flow, there is no (inlet) options. how to use this two module together ( laminar flow and Free Molecular Flow ), or maybe have separate modules appropriate?
*** third question is: how can I choose the right times range in Frequency-Transient?
now I use ( 0 10^{range(-8,5/50,-3)} ) like that example models, but I want to know how to correctly defined and what it depends?

Thanks
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I want to simulate the deformation of two cylinders when they have different potential. Is the model right?

February 15, 2013, 11:37 am
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Hi, guys,
I want to simulate the deformation of two cylinders when they have different potential. Is the model right? In the calucation, I find the model has difficulties to converge.
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Unknown function or operator

February 15, 2013, 11:37 am
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I defined an integration operator intop2 under Model 1 --> Definitions. But when I try to plot the results under Results --> 1 D Plot Group 1 --> Global 4, it says "Unknown function or operator. -Name: intop2 -Plot: glob4 (global)."

What's wrong? Why can't I plot the integration vs frequency?

Thanks.
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Graphene layer - transition boundary condition

February 15, 2013, 1:17 pm
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I am trying to analyze a waveguide with a graphene layer, using Perpendicular Waves - Hybrid Modes.
In this analysis, the graphene layer is considered as an infinitely thin conducting layer.
Thus I need to apply the transition boundary condition at the position of the graphene layer.
The problem that I am facing now is that Maxwell's equations are solved for the magnetic field.
In this case, the tangential components of the magnetic field are forced to be continuous across boundaries.
Consequently, the transition boundary condition for the graphene layer becomes like n x (E1 - E2) = n x (H x n).
I need to solve Maxwell's equations for the electric field,
and I need to use the transition boundary condition like n x (H1 - H2) = n x (E x n).
Could you let me know how to change dependent variables when using Perpendicular Waves - Hybrid Modes?
Or is there anybody who can tell me how to analyze a waveguide with a graphene layer?
Thank you.

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Apparent inconsistency in induction heating solution methods

February 15, 2013, 3:19 pm
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Hi everyone,
I'm new to COMSOL 4.3, and I'm trying to properly use the induction heating module. While modeling the problem of a current loop heating several iron inductors embedded in water in 3D, using either External Current Density or Surface Current, I kept getting temperatures that I strongly suspected were too low. I modeled a similar problem of one inductor in axisymmetric 2D, with the intention of comparing heating via Single-Turn Coil Domain with heating from either of the aforementioned methods. I get a result that seems right to me with Single-Turn Coil Domain, but when I deactivate it and activate either External Current Density or Surface Current, I get a temperature rise of less than a degree, a similar wrong result to what I get with 3D modeling.
With External Current Density, I use the current (1000 A) divided by the cross-sectional area of the loop wire, and I use the current divided by the circumference of the loop wire when I use Surface Current instead.
I've attached the 2D axisymmetric version of the test problem that delivers incorrect results. I've slightly modified the materials such that water has a relative permittivity and permeability both of 1, and an electrical conductivity of 0.1 S/m. Can anyone let me know what I'm missing? Thanks in advance!
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phase change material

February 15, 2013, 4:19 pm
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Hi,
I am working on phase change material. During the simulating the Global Definitions, I can not understand that how step 1(function H) and step 2(function T_right) are working. and how they will affect analytic 1.

regards
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BioHeat transfer in Comsol. I am looking for a programmer for project

February 16, 2013, 12:11 am
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Solved in Comsol using the mesh geometry (3D) some physical three-dimensional problem.

At the exit to the graphical construction solutions: line temperature isotherms in the (O-graphs) can be represented as a 2D (slices, ie a fiber breakdown for Z axis with an interval), and preferably in 3D color (3d not necessarily but advised).

At the entrance of a number of formulas and a table with the values of the coefficients, which depend on the coordinates and time (for the first time izmenyayuschiesyavo time coefficients can be constants).

Performance time-hot task, the faster, the better
money - pay as agreed.

Waiting for feedback and suggestions.
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Rib waveguide

February 16, 2013, 4:54 am
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Hi
I want to simulate this rib waveguide,but when i want to solve the problem the wave scattered every where of the waveguide that it is wrong.It should amplify the center of the waveguide.
Who can help me with it,I need your helps.

Thanks in advance
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Error during compute!! ( please help me!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! )

February 16, 2013, 5:00 am
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