Quantcast
Channel: Latest Discussions - COMSOL Forums
Viewing all 26512 articles
Browse latest View live
↧

Problem in one of the Model Library of Comsol 3.5

March 26, 2014, 10:32 pm
$
0
0
Hey guys,

I'm currently trying the model 'Two Phase Fluid-Structure Interaction' in V3.5's Model Library. You can find this at Model Library-> MEMS Module-> Microfluidics Models->twophase fsi. An animation is also available.

There is one problem however. When I'm following the instructions in 'Modeling Using the Graphical User Interface' step by step, an error message appears as following:
Error:
Failed to find consistent initial values.
Undefined_value_found_Linsolv
NaN_or_Inf_found_when_solving_linear_system_using_PARDISO
And I just cannot figure out why. Could someone help me find it out?

Thank you in advance!
↧
Search

magnetic field

March 27, 2014, 3:40 am
$
0
0
how to calculate the magnetic field in in 3D conductor, what i done is corrector wrong,please help me.
↧
↧

Error in my mesh

March 27, 2014, 4:15 am
$
0
0
Hi,

I am trying to run a model which has 4 different domains, of very varied sizes. I created 3 different meshes - one with larger chunks for the largest domain, a medium one for the medium domain, and a small mesh for the two small domains. After running, I have a "warning" message that says:

No mesh on domain 3
in geometry 1, mesh case 0.
No mesh on domains 2 4
in geometry 1, mesh case 0.
Not all domains are meshed.

I created all meshes and did "build all" for each one before running, so I am not sure why it thinks that some of my domains are not meshed. Does anyone recognize this error and know what it means or how to fix it?

Thanks,
Shoshana
↧

Subtract effective refractive indexes to find birefringence in a planar waveguide

March 27, 2014, 5:19 am
$
0
0
Hi,
I am using the electromagnetic waves module to solve for modes in a square planar waveguide. The waveguide is single mode so I get two modes (TE and TM). I'm doing a parameteric sweep as well so I get pairs of values for each different geometry change. I can find the effective refractive indexs for both modes seperately but can't find a way to subract them to get the birefringence n(TM)-n(TE), which I want to plot.

I know its possible to export the data and do the subtraction offline but I would like to know if its possible to do it in Comsol by possibly subracting table columns or global variables.

Thanks for your help
Peter
↧

post processing parameter sweep?

March 27, 2014, 6:46 am
$
0
0
Hi

Is it possible to run a sweep of surface integrations on a set of parameterized surfaces that are defined

as data sets? More convenient than doing it one at a time. I guess I could define a set of surfaces in a parametric

sweep before running the model.

thanks Dave
↧
↧

Parametric Sweeping a Geometrical Parameter! Possible?

March 27, 2014, 9:34 am
$
0
0
I have a polymer coil in a solid cylinder. This is a reaction-diffusion model. I think usually the materials property or other similar non-geometrical properties are sweeped in parameter sweep.

I want to vary the coil's diameter in parameter sweep. Is this possible? Whats the protocol for meshing for doing this?
↧

Integration over frequency

March 27, 2014, 11:00 am
$
0
0
Hi,

I am designing thin film AR-coatings using COMSOL and I have a question regarding post-processing of results in COMSOL.

After having run the simulation, I obtain a series of S11/S21/S22 etc. responses for different input frequencies which I plot in a 1D graph (1D Plot Group -> Global).

I want to integrate this S-parameter vs. frequency curve to have a single S-parameter value for the full frequency range as opposed to having discrete values at regular intervals.

Currently I'm doing so by exporting the data and then integrating it using Excel or MATLAB.

Is there any chance I could do it in COMSOL without exporting it to windows?

TL;DR I have a simple graph. I want to find the area under the curve without exporting data (image attached).

Thanks

Ahmad
↧

PML problem in groove waveguide

March 17, 2014, 10:41 am
$
0
0
Hi,

I have been trying to simulate the radiation pattern of a small dipole inside a groove carved into a gold substrate (transversal shape is triangular). The simulation box is rectangular, and I set 4 out of the 6 sides to Perfectly Matched Layer (the other two are the basis of the metallic region, which I set to PEC, and the face containing the dipole, where I have PMC in order to set a symmetry plane). The sides where I have PML end in a scattering boundary condition plane.

Although my box is reasonably large, I just don't manage to get rid of the reflections appearing in the electric field (in all directions!! but specially along the axis of the waveguide). I have tried varying PML thickness, PML mesh type, size and distribution, as well as PML scaling factor. I changed from version 4.2a into 4.3 to try the same as well. None of these tries reduced the reflections. Moreover, the field actually seems to be absorbed in the PMLs!! This suggests it may not be a PML problem but a size issue. However, by increasing the dimensions of my simulation box the result don't change either! I know for sure that people is able to solve this problem with smaller boxes than mine in V3.5 so I am quite perplex and don't know where the error might be. Has anyone of you had the same problem? Any clue of what may be going wrong?

Thank you all in advance. Best,

Carlos
↧
Search

Parametric sweep error

March 27, 2014, 1:43 pm
$
0
0
Hi!

I have an issue with the parametric solver. I'm using the joule heating node coupled with the solid mechanics and the electric currents. The model is a beam that is heated by joule effect and transfer heat by the air to a second beam nearby. The solid mechanics is just to obtain the thermal expansion due to the joule effect in both beams, and the electric currents is to obtain the resistance change in the second beam.
My problem is that when I run the parametric sweep varying the voltage applied on the joule node. If I set the parametric sweep from 1V to 10V with 1V step, when it reaches 10V changes the voltage value to 9.5 and then, after a long time, an error appears saying that the solution didn't converged even using the minimum step.
The model dimensions are in um, is part of a MEMS actuator, and the mesh is set to finer.

I'll appreciate any help
Thanks!
↧
↧

Undefined variable error

March 27, 2014, 9:33 pm
$
0
0
How to define a new variable that is a function of other two time dependent variables from two physics in order to use in the equation of the third physic in the model?

I got undefined variable error if writing the expression in variables under definitions of the model, and I cannot use two arguments in the Piecewise function.
↧

problem in comsol program

March 28, 2014, 1:01 am
$
0
0
Hi comsolers,

I defined two projects in comsol in 2D for solving richards equation:
first project: simple rectangle that left boundary was defined as pressure head=0.8 and right boundary as pressure head=0.5, the other two angles= zero flux
and then I made a cross section from these two points from 0.8 to 0.5 (attached cross section as picture1).

Second project: simple rectangle that left boundary was defined as step function for the pressure head from zero to 0.8 =0.8 and from 0.8 to 1.4=0, and for the right boundary pressure head was defined from zero to 0.5=0.5 and from 0.5 to 1.4= 0; the two other angles were zero flux.( attached plots for the left and right boundary as left and right boundary)
Expected results= that cross section for second project for pressure head from 0.8 to 0.5 should be the same as first project.(attached as cross section sample)

Comsol results=they are not like each other!!!!

Do you have any idea that what is the problem in comsol?
Thanks in advance for your valuable comments.
Sepideh
↧

Cannot start up COMSOL 44

March 28, 2014, 1:47 am
$
0
0
Hi,

I have installed both COMSOL 43a and COMSOL 44. I used to be able to use both, but suddenly - after rebooting my computer (I work on Linux) - COMSOL 43a starts up fine, but COMSOL 44 has a problem.
When I go to the log file, I get a long list of error messages.
First a long list of !ENTRY / !MESSAGE errors about org.eclipse.osgi and then a JAVA error "Could not find the COMSOL Application 'com.comsol.guiclient.application'".

How can I solve this?

Example:

!ENTRY org.eclipse.osgi 2 0 2014-03-28 10:36:20.013
!MESSAGE One or more bundles are not resolved because the following root constraints are not resolved:
!SUBENTRY 1 org.eclipse.osgi 2 0 2014-03-28 10:36:20.013
!MESSAGE Bundle update@plugins/org.eclipse.swt.gtk.linux.x86_64_3.8.1.v3834e.jar was not resolved.
!SUBENTRY 2 org.eclipse.swt.gtk.linux.x86_64 2 0 2014-03-28 10:36:20.013
....
....
!ENTRY org.eclipse.osgi 4 0 2014-03-28 10:36:20.017
!MESSAGE Application error
!STACK 1
Exception:
java.lang.RuntimeException: Could not find the COMSOL Application 'com.comsol.guiclient.application'
(rethrown as com.comsol.util.exceptions.FlException)
Messages:
Could not find the COMSOL Application 'com.comsol.guiclient.application'
....
↧

merging interior boundary conditions

March 28, 2014, 3:59 am
$
0
0
Hi all,

I have lines of interior boundary conditions which are made of a lot of small vectors, how is it possible to create one vector as line for the interior boundary condition?

Attached my domain and zoom in section of one line for better recognising the condition.

Thanks in advance for your help.
Sepideh
↧
↧

please help me to measure Voltage,!

March 28, 2014, 5:32 am
$
0
0
HI, I am very new to use COMSOL,
so I wanna ask some problem to proficient person who could use COMSOL,

I'am measuring Voltage from piezo with some stress,
when I measured Voltage from piezo by using probe , applying load,
there is some problem.


Failed to find a solution.
The relative residual (4.3) is greater than the relative tolerance.
Returned solution is not converged.

how to solve this error?
there are some my solutions which I referred some idea from discussion forum

more fine mesh, increasing tolerance, etc,,,
it does not work.

I do not know what I have to do,,,
↧

step function

March 28, 2014, 12:18 pm
$
0
0
Hi,

I am trying to simulate heat transfer problem. I have the values of voltage V_in and Watt density Q_in of the heat source and the heat source is attached under a lid. Now, I want to assign a step function such that when I apply current to the heater, it gets heated to certain temperature Tmax and at this particular time I would like to turn/switch off the current supply, so that the heater temperature goes down eventually. I just want to check the temperature distributionon over the lid to which the heater is attached.

Please let me know how to go about it.
Thanks in advance!!
↧
Search

Plotting local surface integration along a line

March 11, 2014, 8:43 am
$
0
0
Hello,

I have a fluid flow model in a channel that has a rather complex geometry and cannot be sliced up. I'm trying to extricate local flow rates numbers (for the sake of averaging) from along this channel. I was able to do this by creating a parameterized surface that covers only the fluid section in the channel at the inlet, and then "walking" the surface along the channel by manually changing its coordinates. I used a derived integration value to get the actual flow rate (volumetric) out of integrating the local normal velocity over the surface. This was rather tedious and exactly the kind I thing I thought should have an automated solution for somewhere... but I couldn't find any sort of solution/information on how to do this automatically on the web.

Does anyone have any advice on this?

The ideal situation for me would be to cut a 3D line along the channel and then somehow plot the local surface integrations at each of the line's local x values.

Thanks,
-Michelle.
↧

Definite integral calculation

March 28, 2014, 3:02 pm
$
0
0
Hi!

let's say I want to evaluate this definite integral sin(alpha+theta)d_theta from theta=0 to 90 deg where alpha is a known number. How to do that? Alpha is different in every step of the calculation thus integration has to be performed at every step.


Best regards
Rokas
↧
↧

extract data from Comsol to matlab at a specific area

March 28, 2014, 10:09 pm
$
0
0
Hi:
I have a rectangular structure in Comsol and the field is located in the middle of the domain. I want to export only the data at the middle of the domain where the field is located, can I do that in Comsol? or it has to be done through Comsol script?. I used to do post processing manually and select a regular grid directly from Comsol.
Can anyone help me out with this?, I really need to find a way to export as many points from the middle of the domain as possible.
thanks,
Naema
↧

Adding time to an existing project

March 28, 2014, 10:19 pm
$
0
0
In addition to the 15 core teams taking part on this season's HSBC SWS, (those participating in all nine international events on the Series in 2013/2014), [url=www.youtube.com/watch?v=7h1Wcdvy_yo]Hong Kong Sevens 2014 Live Stream[/url] Hong Kong will host a 16th team in the main event and a 12-team international qualifier tournament.


However, in giving the Proteas an almighty scare on Thursday, [url=www.youtube.com/watch?v=L59WxkL6rQg]New Zealand vs Netherlands Live Stream[/url] the Dutch proved that they should not be underestimated in this competition.

Both England and South Africa have not been at their usual best in the ongoing World T20. [url=www.youtube.com/watch?v=fnHVwzN14tE]England vs South Africa Live Stream[/url] While the English side registering a thumping win over Sri Lanka in their last match after losing one against New Zealand, [url=www.youtube.com/watch?v=Fv2Q-slF0x8]South Africa vs England Live Stream[/url] South Africa claimed two narrow wins in the tournament over the Kiwis and the Netherlands.
↧

calculate transmittance using ray tracing

March 29, 2014, 4:13 am
$
0
0
Owe to some optical element are far greater than the wavelength,so I try to use geometrical optics to simulate the light propagate in optical element. But how to calculate the transmittance in it. A simplest problem iswhen a ray passes from air to water, how to calculate the energy of the reflected and refracted light with ray tracing method.
Thanks!
↧
Viewing all 26512 articles
Browse latest View live
Search