IMPOSSIBLE to use COMSOL ++ Video configurations??++

April 12, 2016, 8:52 am

≫ Next: Capacitance is not varying with Body Load

≪ Previous: design a nano structure solar cell in comsol

Hello Everyone!
I added a picture here of how my COMSOL is working... or better saying, not working at all.
I'm afraid I need to buy some video enhancements for my computer to be able to use it.
Anyway... is there any possibility to fix it just by changing some configurations ?
Even If I have poor visualization power, I don't care haha.
I just need to be able to use it properly.

Thank you for your help!
Best Regards,
Thales Machado

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Capacitance is not varying with Body Load

April 13, 2016, 2:09 am

≫ Next: Optical interaction

≪ Previous: IMPOSSIBLE to use COMSOL ++ Video configurations??++

Dear Comsol User,

I am trying to find variation in capacitance between two plates with applied body load. I defined an air box around the plates. I used solid mechanics physics for applying body load. Electrostatic physics for applying bias voltage, applied 1V to the moving plate and fixed plate is grounded. Also I used ALE to couple the two physics, applied free deformation to air box and also applied prescribed deformation and prescribed mesh deformation to moving plate. But the capacitance is not varying with body load.

What changes should I make to get a varying capacitance?
Thank You,
Aswathi M Madhu

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Optical interaction

April 14, 2016, 2:44 am

≫ Next: Solidworks assembly imported into comsol - simulation difficulties

≪ Previous: Capacitance is not varying with Body Load

I want to make a simulation of absorption vs lambda for GaAs at 600nm. I need some example model for this simulation. Plz help me.

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Solidworks assembly imported into comsol - simulation difficulties

April 15, 2016, 11:31 am

≫ Next: Tracking position of isothermal or general contour curve in 1D plot

≪ Previous: Optical interaction

I am a student trying to improve my personal knowledge and skill with Comsol and I have run into a problem while trying to run simulation on an assembly that I've designed. I built the assembly (a small number of small parts) using Solidworks and have imported the parts into comsol. I'm sure everything about the assembly is dimensioned and should fit together correctly (adding/activating pairs in comsol where necessary). However when I try to apply a load, fix the bottom, and compute the simulation, it works on it for ages every time before then coming up with a list of error messages, usually "maximum number of iterations reached" and "the relative error is greater than the relative tolerance". I've played around with the settings of the study to see if I could work it out but no luck yet.

Any advice will be appreciated!

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Tracking position of isothermal or general contour curve in 1D plot

December 4, 2013, 4:24 am

≫ Next: Issues with Pipe Flow and Surface Radiation interaction

≪ Previous: Solidworks assembly imported into comsol - simulation difficulties

Hi everyone,

I have very simple model where copper plate is heated by a pulsed laser (transient study, 2D, see file surfaceplot_1).
Now, I am searching for a way to track the position/depth of my melting and vaporisation temperature over time during the laser pulse.
I would like to have a 1D plot at the defined x-position (e.g. the center of the pulse) where I can see the y-coordinate of my isothermal (T_melt or T_vap) as a function of the time (meaning y = f (T_melt, t) or y = f(T_vap, t)).

I know that I can plot defined isothermal curves in a contour plot and than manually extract the position of the the curve at a corresponding position for each time step which is however very inefficient (see file contourplot_1).

I have been playing around with 1D cuts etc. trying to get what I need, however not very successful so far. I could setup a number of points along y at a certain x-position and the plot the temperature of each point over time the get an estimate of the depth evolution of my defined temperatures. However, this also doesn't really hit the point.

Any ideas/hints would be greatly appreciated.

Best wishes
Christian

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Issues with Pipe Flow and Surface Radiation interaction

April 21, 2016, 5:52 am

≫ Next: Capacitively Coupled devices (Pixel detector)

≪ Previous: Tracking position of isothermal or general contour curve in 1D plot

Hello Comsolers!

I am very new to the program, and I am having some issues regarding Non Isothermal Pipe Flow, Heat Transfer in Solids, and Heat Transfer with Surface to Surface Radiation.

I have a 1D pipe circuit, where the the inlet and outlet (plus 1 meter pipe for each of them) sections are resting on top of a block of soil, and the rest is buried underground. There is a flow of water in the pipe.

The main idea is to simulate the pipes being heated by the Sun's radiation, observe an increase in temperature in the pipe, and observe how the ground is being heated by the thermal transfer between the fluid-pipe-ground.

For some reason, I am not observing a Radiation - Thermal transfer interaction, and I do not know what am I doing wrong.

Here's the boundaries that I have:

For Surface to Surface Radiation: Defined an external radiation source by solar position, a diffuse surface and heat flux (both of these only on the side of the block that is illuminated by the Sun), defined a constant temperature at the base of the block of soil (which is not illuminated).

For Non Isothermal Pipe Flow: Defined an Inlet with a volumetric flow rate, a Heat Outflow at the outlet, and a wall heat transfer with internal film resistance.

For the Heat Transfer in Solid, I have defined a Heat Flux in all applicable domains.

Any help is greatly appreciated! I can provide more details if needed.

Thank you all,

Aaron

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Capacitively Coupled devices (Pixel detector)

April 22, 2016, 6:15 am

≫ Next: Plotting the mesh of a cut plane through a 3D model

≪ Previous: Issues with Pipe Flow and Surface Radiation interaction

Hi all,

I am new at COMSOL and I have been struggling to find how I can perform the simulation and extract the results that I need.

Problem:
I work at ATLAS/CERN and I need to simulate a appreciatively coupled pixel detector that we are studding.
Basically we have a pixel sensor glued to a readout chip.
You can imagine the pixel sensor as some copper pads isolated of each other by an insulator. Under these pads, on the other side of the glue, there is the pads of the readout chip.
If you think about an 3x3 matrix on both sensor and chip, I need to simulate how the charge, or voltage, changing in the middle sensor pixel will affect the other 9 pads in the readout chip.
Basically, a matrix of parallel plates capacitors and I need to check the cross capacitance.

Where I am:
I already have a complete 3D model of the detector (form SOLIDWORKS) and I already positioned everything in COMSOL (materials; terminals and ground, and etc...).
For that I am using the electric currents physics with a small-signal analysis, frequency domain study.
I am able to see the electric fields and potential.

Does anyone know how to extract the cross capacitance or a good reference material for that?
Attached there is a picture of the cross section of the device. It shows 1/4 of the chip if the octagonal pads of the sensor, on top, and the pads of the readout chip exposed on bottom.

Many thanks in advance.

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Plotting the mesh of a cut plane through a 3D model

March 20, 2013, 12:06 am

≫ Next: Combine two solutions

≪ Previous: Capacitively Coupled devices (Pixel detector)

Hey guys,

So i am currently doing some simulation involving parallel plate capacitors and i just want to see the difference between the meshes outside and within the capacitor.

I've tried to create a plot of the mesh in the "results" section but there isn't a way for me to plot the mesh. I can only plot from the "solutions". Am i approaching this from the wrong direction? Is there a way i can maybe direct the cut plane to take its "data" from the "mesh"? Any ideas guys?

I hope my questions are clear enough.

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Combine two solutions

February 5, 2016, 8:53 am

≫ Next: Patch antenna with a coat of Microwave absorber

≪ Previous: Plotting the mesh of a cut plane through a 3D model

Hey all,

I have two consecutive time dependent studies and two solutions sol1 and sol2. In postprocessing I would now like to "stitch" these two solutions together, so that instead of having to deal with two data sets sol1 and sol2 I just have one data set solComb that contains the combination of these consecutive two solutions.

I want to be able to access the time(1) which lies in sol1 and time(6) which lies in sol2 with just one data set.

Thanks in advance for your help

best

Paul-Remo Wagner

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Patch antenna with a coat of Microwave absorber

April 26, 2016, 11:17 am

≫ Next: Mesh size and dimension of the structure

≪ Previous: Combine two solutions

Hi,
I am studying the improvement in absorption of radiation by microstrip patch antenna, which is coated with a layer of microwave absorber that I am going to develop.

How can I define the physics for this absorber?

Thanks in advance,

Best,
Karthik

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Mesh size and dimension of the structure

April 27, 2016, 10:14 am

≫ Next: Exporting data while solving

≪ Previous: Patch antenna with a coat of Microwave absorber

Hi Guys,

I am quite new in COMSOL, and I have three small questions about the setting of the mesh in ewfd, frequency domain study.

1. I found the results will be different if I used different size of the mesh, in this case, how could I value the setting of the mesh is suitable or not?

2. Another problem, the different dimension of my waveguide with same mesh size will also yield different results, how could I determine the right size of mesh if I change the length of my waveguide?

3. The distance between the light source and the boundary to my waveguide will also get different results, how could I choose the distance of the boundary to my waveguide.

Is there anyone have good suggestions? it would be very appreciated.

Chuan

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Exporting data while solving

April 29, 2016, 6:02 pm

≫ Next: Tracking Residual

≪ Previous: Mesh size and dimension of the structure

Hi,

I am relatively new to COMSOL. Is there anyway to write the data generated up to a point while solving into an external file like excel or .txt which can be opened in COMSOL at a later point of time?
I have come across discussions to export data while solving in case of a parametric sweep, but nothing to go on in terms of writing data generated as it is being solved.
This way, instead of letting the data go as a waste, at least a partial solution can be retained.

Thank you.

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Tracking Residual

April 3, 2011, 12:10 pm

≫ Next: Animation Scale Factor

≪ Previous: Exporting data while solving

I need to track the residual in my simulation in order to represent how closely the governing equations are being represented. I know comsol keeps track of residual since ive had several errors referring to it. Post processing doesnt have residual as a specific plotting value as far as i know.

Do i need to use a specific solver which uses residual? Does any one know how to access its value? I can use matlab live link if necessary.

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Animation Scale Factor

April 18, 2011, 10:24 am

≫ Next: Energy Fluxes in Conjugate heat transfer Example.

≪ Previous: Tracking Residual

I'm trying to create an animation of my simulation.

Every time I create it (under Report > Animation), the scale factor is reactivated to some arbitrary value EVEN if I deselect it or specifically tell COMSOL that I don't want any scaling (i.e. scaling factor = 1).

I tried in 2D Plot Group 1 > Surface 1 under "Inherit Style" to uncheck the "Deform scale factor" but every time I export my animation, this gets automatically checked again.

I tried in 2D Plot Group 1 > Surface 1 > Deformation 1 under "Scale" to put a scale factor of 1 but when I export my animation, it gets automatically changed to an arbitrary value.

Question: How to create an animation that actually include the deformation BUT to its real value (i.e. Scaling Factor = 1)?

I tried a "Reset History" and rebooting COMSOL but it still gets back to some annoying scaling factor.

Anyone has any ideas how to deactive this?

Thanks.

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Energy Fluxes in Conjugate heat transfer Example.

April 21, 2011, 11:00 am

≫ Next: Using deformation results as initial conditions for the next study

≪ Previous: Animation Scale Factor

Hi,

I want to verify that my energy and mass balances across the boundaries in my models are right.

Can any of you post a very simple example of a conjugate heat transfer model (laminar or turbulent) showing the proper way to do it?

I tried with surface integration, but the figures don't seem to match my inputs. Maybe I am selecting the wrong variables to integrate.

Thanks,

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Using deformation results as initial conditions for the next study

August 22, 2012, 3:55 am

≫ Next: How do I retrieve cross- and co-polarization T/R data from heterogeneous periodic structures in 3-D?

≪ Previous: Energy Fluxes in Conjugate heat transfer Example.

Hi all,

I have a linear elastic model with a stationary study whereby I apply a boundary load and deform the model domain - this is simple and works fine.

Next, I would like to use the deformed results from the first solution as the initial condition for a second solution where I re-apply the same boundary load. I hope to be able to see that the deformation builds up with each successive solution/load (I plan to repeat this 10 times eventually).

**However, I would like to know how to take the deformed results from the first solution and set them as the initial condition for the next solution?** and **Is it possible to alter the geometry as part of this, as the boundary with the boundary load is bound to deform too?**

Any help would be greatly appreciated!

Cheers, James.

"Using deformation results as initial conditions for the next study"

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How do I retrieve cross- and co-polarization T/R data from heterogeneous periodic structures in 3-D?

December 10, 2013, 11:25 am

≫ Next: How to set all graphics altogether from different models

≪ Previous: Using deformation results as initial conditions for the next study

COMSOL'ers:

I have a complex periodic array structure (dipole on substrate on ground plane) illuminated by an oblique plane wave. If I were to define an incidence plane (say x-z plane) and launch a TM mode wave along this plane (k(x,z) and H(x,y)=Hy), then how can I separate the results into their co- and cross-polarized components? If I were to extract a reflectance from the S11 parameter, it would consist of the reflected energy from along both polarization basis vectors (x and y). I would like to isolate these responses, to identify what, if anything, is coming from a rotation of the incident field upon interaction with the structure.

Calculating some sort of ratio of abs(Ex)^2+abs(Ez)^2 and abs(Ey)^2 to abs(normE)^2 gives me some sort of indication of co- and cross-pol, respectively, but it doesn't seem to be a true answer. Any thoughts?

Thank you for your time and consideration!

-Bryan

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How to set all graphics altogether from different models

June 19, 2016, 7:30 am

≫ Next: Can I use the explicit selection in "dom"?

≪ Previous: How do I retrieve cross- and co-polarization T/R data from heterogeneous periodic structures in 3-D?

Hello,
Please I need to find a way out for graphing multiple graphic results "2D plots" of different models altogether.

The subject is changing the core circle radius in PCF and plotting the corresponding electric field intensity vs a 2D cutline from the center till the end of the cladding radius in a 2D plot line for several radii

Thank you!

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Can I use the explicit selection in "dom"?

June 21, 2016, 8:16 am

≫ Next: No Matlab Livelink response after loading model to Matlab

≪ Previous: How to set all graphics altogether from different models

I have got several geometries in which I have to define different subdomains. I may not have some much pain to define an explicit selection for the subdomains. But when it comes to the assignment of materials or afterward postprocessing, I have to use A*(dom==1 || dom==2 ... on and on). It is really painful to find which number a subdomain is pertaining to.

Can I just use A*(dom == sel1), where sel1 is a predefined explicit selection set? I tried to but it failed. Any ideas or suggestions?

Venn Wu

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No Matlab Livelink response after loading model to Matlab

June 23, 2016, 10:49 am

≫ Next: How to plot 2 graphics from 2 Time Dependent Steps altogether ?

≪ Previous: Can I use the explicit selection in "dom"?

Hi there,

I have a large Comsol 4.3a model with size almost 50 GB. I would like to run it through MatLab to export all solution data from parametric sweep simulation with almost 1,300 parameter combinations. The problem is that MatLab cannot step to the next script even though its status is busy after finishing loading the model using the following script.

addpath '/cluster/cloud/comsol-43a/mli'
import com.comsol.model.*
import com.comsol.model.util.*

mphstart
ModelUtil.showProgress(true);
model=mphload();

I'm guessing that the model size is too large and there is some limitation on Java about size in the settings. Does anyone know how to solve this problem?

Thanks,
Mengxue

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