Multiple user in Linux?

May 7, 2013, 5:26 am

≫ Next: Using a 2D eigenvalue solution as a scattering boundary input in a 3D simulation

≪ Previous: How can I define an PML in model solids mechanics ?

$

0

0

Hi,

since some time I use Comsol on a Linux machine. Because of some former trouble I changed the directory used for temporary files to my home directory (followwing the advice given in solution number 1083). Recently another user got an account on the machine, but he was not able to start Comsol. I gave him full access to reading, writing and executing in the directory used for the temporary files. However the following error message appears when he tries to start COMSOL:

"Locking is not possible in the directory "/home/sabine/Comsol43/comsol43data/configuration/comsol/org.eclipse.osgi". A common reason is that the file system or Runtime Environment does not support file locking for that location. Please choose a different location, or disable file locking passing "-Dosgi.locking=none" as a VM argument.
Permission denied"

Does anyone know what to do?

Thanks a lot

Sabine

---

Using a 2D eigenvalue solution as a scattering boundary input in a 3D simulation

May 7, 2013, 5:41 am

≫ Next: Laminar Flow +Chemical Reaction

≪ Previous: Multiple user in Linux?

$

0

0

Dear all,

I have a simulation that solves for a whispering gallery mode in a toroidal geometry. This is done using a 2D PDE solver. This file is attached and is adapted from Mark Oxborrow's work: sites.google.com/site/markoxborrow/axsym.

I want to take this 2D solution, and let it propagate from a boundary into a fully 3D electromagnetic wave simulation. Is there anyway to accomplish this?

Thanks,

Matt

Laminar Flow +Chemical Reaction

May 7, 2013, 6:26 am

≫ Next: Parametric Study making functions

≪ Previous: Using a 2D eigenvalue solution as a scattering boundary input in a 3D simulation

$

0

0

Hi,

Can anyone please help me with my model and guide me as to where I am going wrong. I am trying to simulate a simple chemical reaction A+B-->C in a pipe filled with water flowing at laminar velocity. I create a laminar flow profile using Laminar physics which I used as my input velocity to the Transport of Diluted Species physics. I verified that the Laminar and Transport physics are coupled.

When I plot the concentration profile, there is no change in the reactant or products concentrations. They remain the same, meaning there is no reaction.

I have defined the reactions rates in the variables section of the model. I dont know if I am plotting it wrong or what is the issue.

Please Please help. I dont know where I am going wrong. I cleared all solutions and meshes as I was not able to upload the file with them due to size limit

Thanks,
Romani

Parametric Study making functions

May 7, 2013, 7:11 am

≫ Next: New version

≪ Previous: Laminar Flow +Chemical Reaction

$

0

0

Hi there,

I am doing a parametric study with a variable T_initial for a frequency domain simulation for a fixed range of frequencies, this worked well

I need now to change the set of frequencies with a function freq_range(T_initial). In the study frequency-domain it always says failed to evaluated the function. The function was defined in the global definitions and it is plotted well in the results.


The field frequencies does not accept my function I dont know why.

New version

May 7, 2013, 7:16 am

≫ Next: Brinkman Equation; Anisotropic Permeability

≪ Previous: Parametric Study making functions

$

0

0

I have a model which I created in 4.3a and that ran OK in 4.3a. I have updated to 4.3b today, but the model won't run :(

I get various errors including:
Failed to evaluate operator Jacobian.
Failed to evaluate operator Jacobian.
- Operator: mean
- Geometry: 1
- Boundary: 5 6 7
Mean operator requires an adjacent entity of higher dimension.
Failed to evaluate variable Jacobian.
- Variable: mod1.v
- Geometry: 1
- Boundary: 5 6 7 8 9 10 17 20 24 31 32 33 34 47 48 49 50 51

I have tried to reopen the model in 4.3a but it won't open as it was saved in 4.3b. Is there anyway I can get round this? There is obviously something that 4.3b doesn't like in the model and I don't want to have to create the model from scratch again as it's pretty complex.

Brinkman Equation; Anisotropic Permeability

May 7, 2013, 10:36 am

≫ Next: Thermoelectric Model

≪ Previous: New version

$

0

0

Can I specify an anisotropic permeability with COMSOL 4.3a; Subsurface Flow Module; Brinkman Equation?

When I go to user defined, I can assign a single value only. I can't enter a tensor or specify "Diagonal, anisotropic or symmetric". Please let me know if you have a way to do it.

Thank you very much,

Thermoelectric Model

July 12, 2010, 12:23 pm

≫ Next: Which solver for time dependent : Electromagnetic Waves + Solid Mechanics

≪ Previous: Brinkman Equation; Anisotropic Permeability

$

0

0

Dear All,

I am looking to find and study example models relating to thermoelectric effect modeling using COMSOL.

Does anyone have any reference source/model on thermoelectrics which could be used ?

Thanks
Piyush

Which solver for time dependent : Electromagnetic Waves + Solid Mechanics

January 20, 2012, 1:44 am

≫ Next: Free and porous media flow 3D simulation - convergence issues

≪ Previous: Thermoelectric Model

$

0

0

Dear all,

I am faced with a tricky problem for me, on which I cannot find a solution in the documentation. My model is representing a polymer that, subjected to some laser beam, expands in illuminanted area. So the geometry is changing with time : at t=0, the light is more intense in some places. t+1 the polymer deforms, and so induce a different light absorption pattern.

I thus have RF + Solid mechanics + Moving mesh modules. If I run a frequency analysis on the RF, I see the instensity of light being absorbed through the polymer. Then, if I run a stationnary study on the object, it deforms accordingly.

But both studies are not coupled, and I need to run 10 or more (who knows) studies like that (frenquency then stationnary) to get an idea of the real stationnary state.

My question is : is there a way to couple EMW and a moving structure with some study type? I discovered the "Frequency Stationnary" one, but it's only used with Joule heating, which is not the case here.

[Edit] : I read that : www.comsol.com/community/forums/general/thread/20275/ but couldn't find any positive answers.

---

Free and porous media flow 3D simulation - convergence issues

February 18, 2012, 7:21 am

≫ Next: Magnetic flux density

≪ Previous: Which solver for time dependent : Electromagnetic Waves + Solid Mechanics

$

0

0

hey all,

I was using the free and porous media flow module (fp) to understand flow distribution patterns in my system. in the 2-D form it was working pretty neat. When I scaled it up to a 3D problem, its giving me all sorts of issues. Any comments/suggestions on the nature of solver that I can use for such a problem. I've tried different meshing options too. The solver isn't able to converge for any of those options.

Thanks,
Rohini

Magnetic flux density

July 11, 2012, 12:22 am

≫ Next: What is convergence?

≪ Previous: Free and porous media flow 3D simulation - convergence issues

$

0

0

in the model attached i excited the coil by single turn coil domain , but i am getting only the magnetic flux density on first coil only , not reaching the second coil can any one pls solve the problem , i am not bale to attach the model as it is very high size

--
kishore Naik Mude

What is convergence?

March 10, 2013, 7:37 am

≫ Next: Solidworks model meshing issue

≪ Previous: Magnetic flux density

$

0

0

I'd just like to know what convergence is - in the context of COMSOL.

Solidworks model meshing issue

March 26, 2013, 11:35 pm

≫ Next: Magnetic-structural coupled analysis, result not good

≪ Previous: What is convergence?

$

0

0

I created geometry of a saddle coil pair in Solidworks and then I imported it to COMSOL using the geometry import option. When I build meshes, it gives error of meshing around edges and corners.

COMSOL imports edges and surfaces. How can I import the part as a solid geometry?

I used livelink for solidworks too and got the same error.

Magnetic-structural coupled analysis, result not good

April 18, 2013, 8:22 am

≫ Next: De-icing of wing

≪ Previous: Solidworks model meshing issue

$

0

0

This is part of my thesis. I'm trying to simulate the magneto-structural coupled analysis on a magnetic gear. The attached file is a picture of my result.

The cylinder consists of permanent magnets and steel, which can be treated as a rotor. The single bar is also made of steel. It is static analysis. I just want to modulate the maximum of the single steel rod's deflection.

The three physics I used for coupled analysis is : AC/DC no current, Structural, ALE.

The FEA result on steel rod deflection is half of the experimental result. I'm wondering if I'm setting the wrong mesh. I use "Free Tetrahedral". Set the mesh as 'user controlled mesh'. Should I use "Physic controlled mesh" when ALE is used?

I'm thinking if I should use 'swept mesh'. Yet it not worked when I try to mesh the air region.

Thanks.

De-icing of wing

May 4, 2013, 1:05 pm

≫ Next: Error in inductor modelling with Magnetic fields interface

≪ Previous: Magnetic-structural coupled analysis, result not good

$

0

0

Hi,
I'm doing simulation of deicing of wing due to heating up sections of the leading edge of the wing. However, when I go through all the boundary set up and run the solution. I get an error:

Undefined value found.
- Detail: NaN or Inf found when solving linear system using SOR.

I've attached my file to this, please help me eliminate this if possible. Few possibilities of error might be at how my velocity is set up: i want it in -y direction but I'm not sure if that will cause any problems or not.

Error in inductor modelling with Magnetic fields interface

May 6, 2013, 12:44 am

≫ Next: Question about "if" function

≪ Previous: De-icing of wing

$

0

0

Dear all,

I'm using the Magnetic fields interface on an inductor model I'm currently working on. The idea is to do a multiphysics coupling with Heat transfer in solids so that I can compare it with results I've achieved using the Induction heating interface. My model is very similar to a tutorial model called "single_coil_boundary_feed" (www.comsol.com/showroom/documentation/model/14067/), and the physics are setup in exactly the same way. The difference is that my model has 17 turns instead of only one that we have in the tutorial model.

When I run a simulation only consisting of the coil and an air domain around it, I have no issues at all. But since this is supposed to be a more detailed model of an inductor I would like to incorporate a core (a very simple, rectangular box in the middle of the windings) and a circular shell surrounding the inductor.

However, when I try incorporating the shell the simulation won't converge. The error I'm getting is "Failed to find a solution. Divergence of the linear iterations. Returned solution is not converged". I've tried with a more detailed mesh and that doesn't solve the problem. I've also tried using a non-zero conductivity of the air and that doesn't do the trick either. I haven't tried incorporating the core yet since I suspect that it will also give the same error. I have no idea what the problem could be, so I really need your help.

Best regards
Bilal

---

Question about "if" function

May 6, 2013, 6:44 am

≫ Next: comsol 4.2a with matlab R2011a

≪ Previous: Error in inductor modelling with Magnetic fields interface

$

0

0

Hello,

I want to add a volume force to NS equation with a special condition.
The volume force is like this: H/Re
Re is reynolds number.
u2 is calculated from convection-diffusion equation and I want to limit the values of u2 like this.

if (u2>=0 or u2<=1) then H=u2
if (u2>1) set it to 1 and then H=u2
if (u2<0) set it to 0 and then H=u2


Would you please help me?
Thanks,
Hooman

comsol 4.2a with matlab R2011a

May 7, 2013, 9:01 pm

≫ Next: 2D Poiseuille flow, wrong solutions?

≪ Previous: Question about "if" function

$

0

0

Hi,
I saved the comsol file in matlab as told. The tutorial says open ''COMSOL with MATLAB''. What does that mean?
Also i get an error as follows when i run the m file of the comsol model.

Undefined variable "ModelUtil" or class "ModelUtil.create".

Error in ==> modelmfile at 10
model = ModelUtil.create('Model');

2D Poiseuille flow, wrong solutions?

May 7, 2013, 11:21 pm

≫ Next: Wedge-on-Mirror !!

≪ Previous: comsol 4.2a with matlab R2011a

$

0

0

Hello all COMSOL users!

I was solving a simple 2D Poiseuille flow problem on a rectangle domain. I use the "creeping flow" physical model with the "incompressible" option. And I just set the boundary condition of the inlet and outlet with two different pressure values with the options "pressure, no viscous stress" and "pressure" respectively. And I just leave the other two boundaries "no slip".

But I think I got wrong answers when solving this problem, because the pressure varies with not only x but also y near the inlet. This can be seen in the contour plot of pressure. However, as is well know, pressure should be just a function of x in this situation, and so the contour plot of pressure should be a set of vertical lines all over the domain.

So I am wondering why I got the wrong answer? Did I apply wrong boundary condition at the inlet? I got confused, because there is no other options relating to pressure can be chosen in the inlet setup menu.
Any comments will be grateful.


Pai Liu

Wedge-on-Mirror !!

May 8, 2013, 3:54 am

≫ Next: Export data as .csv or .dat

≪ Previous: 2D Poiseuille flow, wrong solutions?

$

0

0

Hello,,

How can we design a glass wedge layer tend a 0,5 degree angle from a thin layer in the mirror cylindrical at 3D space ?

Export data as .csv or .dat

May 8, 2013, 6:29 am

≫ Next: Temperature Gradient 'flip'

≪ Previous: Wedge-on-Mirror !!

$

0

0

Hello,

I am working on a 2D transient problem. I have the results and want to post processing them.
I can easily export data in those formats(csv or dat) and open in Matlab or Excel.
I want to select just a part of data. as my domain in big, the exported file size is big(more than 2G).
Is there any way to export just a part of domain and specific time and my variable magnitude (suppose temperature)?
So in the file I need to have the data for x,y,t(time) and my calculated variable(like temperature).

Any idea?
Thank you in advance!