AC/DC Module - Latest Discussions - COMSOL Forums

Designing Voice Coil Actuator with Flexures

Fri, 18 May 2012 00:54:41 +0000

Hi,

I am new to comsol and am trying to design a linear voice coil actuator by fixing each end to two diaphragm flexures, therefore keeping everything axisymmetric. I have designed the flexures with the structural mechanics and have placed loads and found eigenfrequencies. I am wanting to know how to incorporate a voice coil actuator to drive the flexures? I searched for some similar models without any luck. The ideal setup would be applying some step function to the voice coil and get the response of the system, and tune it with a PID controller. Any help whatsoever would be great as I am just getting used to the new software.

Thanks!

3D coil inductance with frequency domain

Thu, 17 May 2012 13:28:28 +0000

I modeled a coil to calculate the inductance in both 2d symmetric axis and 3d with frequency domain. It gives a rise an issue that the value of calculated inductances are different.

Since there is no directly option for inductance in 3D, I use the following fomula:
L=N*flux/I0
L: inductance
Flux: integration of magnetic flux density over a closed surface
N: number of turn
I0: the applied current

The value of inductance in 2D is equal to 5.0408e-5H, while in 3D is 4.226e-5H.
However, it gets closer to results from 2D when I changed frequency domain to stationary domain in 3D which is 5.0803e-5H.

Can anyone give me a favour?

Regards,
Hongyu Li

analyze movement of particles in ACDC

Thu, 17 May 2012 12:22:26 +0000

Hello everyone

I have a question and I wondered if anyone can give me some info.
I am using AC/DC module right now. However I want to add movement of A charge in my model and analyze the effect of its movement on electrical field of whole system.
Do you think it is possible to do these kind of simulations by using time dependent analysis? Because I have checked different models here that use time dependent analysis but their goal was totally different from mine.
I think in order to do this I should have access to particle tracing module. Am i right?
I would be really grateful if someone can give me some information or give me a link of example related to this.

Best
Bahar

Nonlinear electric conductivity

Thu, 17 May 2012 02:18:31 +0000

Hi,

I'm currently working on electrical transients simulation using AC/DC module. How can I define nonlinear electric conductivity of zinc oxide (ZnO) in subdomain settings?

Thank you

Magneticfield simulations of a Nanodevice

Wed, 16 May 2012 07:14:06 +0000

Hi Ivar

My name is Daniel Sandermann and I am a student at the University of Copenhagen. As the title shows I am trying to make a simulation of how the local magnetic fields will look like, if I have a Nanodevice made out of Cobalt (ferromagnet) which will then be subjected to a 1.8T magnetic field. The method I have been using is as follows:
mf->Amperes law->Remenant field of 1.8T in Y-drection. This has given me some decent 3D simulations of how the field will look like. So here are my guestions:
1) Is there a more efficient way of setting up the model? What we are basicly interested in, is to see the local fields at 67nm below the device

2) I would also like to make 1D plot of the Remenant field as a function of the distance below the device. But havent really been able to do it.

Hope you have the time to help me, it would really be appreciated.

Best Regards

Daniel Sandermann

simulation of eddy current damper

Wed, 16 May 2012 03:59:16 +0000

hi all
i am working on eddy current damper....in which beam (cantilever type) vibrations (free) are to be damped...the material of beam is aluminium....i have simulated the two electromagnets..but i am not able to simulate the beam vibration with initial conditions @t=0 displacement of free end is 0.003m and velocity =0. i have used the eigen frequency study but the tip displacement is very large as per our initial condition....when i used the time dependent study it gives an error of singular matrix...and one thing more should i use the moving mesh for beam...

plz help

i've attached the model...

Thanks and regards
Mohit

Simple convection model not converging

Tue, 15 May 2012 13:12:31 +0000

Hello all,

I have a simple beam model in which the beam is made out of silicon and it is sorrounded by air. When I apply a voltage to the beam, it creates temperature gradient along the beam due to the resistivity of the beam being dependent on the temperature at which it is at. To incorporate the convection due to the air, I went ahead and used two physics to mimic this phenomenon: electric currents (to compute the resistance of the beam and the power) and non-isothermal flow (to compute the temperature, including the effect of convection). The model itself is a one quarter model, allowing for symmetry, which I took care of with the simple boundary condition of electric and thermal insulation. The reason behind coupling these is so that I can see the effect of convection, given the fact that the heat transfer coefficient of air will change due to temperature. When I run my model with time dependent I get the following error:

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

When I run it with stationary I get the following error:

"Failed to find a solution.
Maximum number of segregated iterations reached.
Returned solution is not converged."

Any help is greatly appreciated.

Thanks.

boundary settings- Thin layer (surface thickness)

Fri, 11 May 2012 17:28:17 +0000

Hello everyone

I have a question about settings for boundary conditions. In most of physics, when you use 3d and you want to define a boundary condition like dielectric shielding for one surface there is one option called "Thin layer".
For this "Thine layer" you should define "Surface thickness" which is by default 1m.
My question is that what exactly this surface thickness means? because it seems it can affect my results a lot.
I know it is not thickness of my domain (if the domain is a cube with dimension of 0.1 um). So what exactly is this? I went through some tutorials and i couldn't find any explanation.

Best
Bahar

Complex Dielectric Permittivity

Fri, 11 May 2012 11:04:59 +0000

How can we insert complex dielectric permittivity as function of frequency in Comsol.
How can we plot Cole-Cole Plot in Comsol

Poisson equation, current source

Fri, 11 May 2012 09:18:10 +0000

Dear Comsol community,
I was wondering if it's possible, using the Poisson equation PDE, to have a current source instead of a potential one.
Thanks for your time, regards,
Giorgio.

Postplot calling an external matlab function --> no plot

Thu, 10 May 2012 18:29:06 +0000

Hello, (this was sent to COMSOL support, too.)

I'm having an issue in version 3.5a using postplot function: in matlab, when postplot tries to surface plot a function that is defined as an external matlab function, a figure window opens but no plot appears. There, I notice that matlab uses 100% CPU resource. What could be the problem?

Here is a specific scenario that I tested:

- In a 2D electrostatics setup, make some region (subdomain) between two constant-potential boundaries have a spatially-varying permittivity defined as an external matlab function.
- Solve for the potential V (done in 'comsol matlab' environment).
- Save the project as a .m file
- In matlab, load the .m file
- Try making these plots:

1. Plot the solved potential V via

h=postplot(fem,'tridata','V');

A correct plot of potential distribution appears.

2. Plot the permittivity via

h=postplot(fem,'tridata','epsilonr_emes');

Matlab goes to work (100% CPU usage), but no plot appears (indefinite wait).

This behavior was observed in both linux and windows versions.

What could be the problem?

Thank you in advance,

Do-Hoon

Metal-Insulator boundary

Thu, 10 May 2012 12:39:16 +0000

Hello everyone

I have a question about boundary conditions.
I have 3 layers (Insulator-metal-insulator) and this structure is placed in a solution that i want to sense its voltage with that metal layer.
Insulators are SIO2.
The problem is that when i choose dielectric shielding for insulator boundaries, the voltage on the metal, insulator and the solution will be all the same (and i was expected that it should not be the same on insulator layer!)
So i thought may be i should choose ground for insulator (!) and then the problem is solved. I have zero on insulator, different voltages on metal, and in solution.

But i beleive there is something wrong and i shouldn't work like this. Anyone has any idea?

Best
Bahar

linux cluster distribute computing no speed up

Wed, 09 May 2012 01:50:39 +0000

cluster configuration:1head node+8nodes，32cores each node，64GB ram each node。

comsol：comsol4.0 floating network licence installed on the head node, intel mpi

mpi file: COMSOL40\models\ACDC_Module\Verification_Models\parallel_wires.mph the air domain is increased in order to get more DOF, stationary study, direct solver MUMPS
test process:
Step 1. Solve this problem in 1 node using 16 cores
Step 2. Solve it in 4 nodes using 16 cores each node

test result: the solution time is almost the same (about 100 seconds), no speedup is obtained. It seems that all the nodes do the same thing.

Please check the folowing logs and help me out please, Thanks a lot.

PBS log for Step 1
------------------------------------------------------------------------------
--- Starting job at: Wed May 9 10:58:22 CST 2012

--- Current working directory is: /home/lubo/comsol
--- Running on 16 processes (cores) on the following nodes:
16 node5
--- mpd BOOT
/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 mpd boot -f /var/torque/aux//1723.mgmt -mpirsh ssh --verbose
running mpdallexit on node5
LAUNCHED mpd on node5 via
RUNNING: mpd on node5
--- mpd TRACE
--- Parallel COMSOL RUN
/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log
--- mpd ALLEXIT

--- Job finished at: Wed May 9 10:59:57 CST 2012
--------------------------------------------------------------------------------------------------------------------------------------------------------------- Starting job at: Wed May 9 10:58:22 CST 2012
--- Current working directory is: /home/lubo/comsol--- Running on 16 processes (cores) on the following nodes: 16 node5--- mpd BOOT/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 mpd boot -f /var/torque/aux//1723.mgmt -mpirsh ssh --verboserunning mpdallexit on node5LAUNCHED mpd on node5 via RUNNING: mpd on node5--- mpd TRACE--- Parallel COMSOL RUN/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log--- mpd ALLEXIT
--- Job finished at: Wed May 9 10:59:57 CST 2012--------------------------------------------------------------------------------------------------------------------------------------------------------------- Starting job at: Wed May 9 10:58:22 CST 2012
--- Current working directory is: /home/lubo/comsol--- Running on 16 processes (cores) on the following nodes: 16 node5--- mpd BOOT/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 mpd boot -f /var/torque/aux//1723.mgmt -mpirsh ssh --verboserunning mpdallexit on node5LAUNCHED mpd on node5 via RUNNING: mpd on node5--- mpd TRACE--- Parallel COMSOL RUN/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log--- mpd ALLEXIT
--- Job finished at: Wed May 9 10:59:57 CST 2012------------------------------------------------------------------------------

PBS log for step 2

------------------------------------------------------------------------------
--- Starting job at: Wed May 9 11:04:36 CST 2012

--- Current working directory is: /home/lubo/comsol
--- Running on 64 processes (cores) on the following nodes:
16 node5
16 node3
16 node2
16 node1
--- mpd BOOT
/home/lubo/comsol/COMSOL40/bin//comsol -nn 4 mpd boot -f /var/torque/aux//1724.mgmt -mpirsh ssh --verbose
running mpdallexit on node5
LAUNCHED mpd on node5 via
RUNNING: mpd on node5
LAUNCHED mpd on node3 via node5
LAUNCHED mpd on node2 via node5
LAUNCHED mpd on node1 via node5
RUNNING: mpd on node3
RUNNING: mpd on node2
RUNNING: mpd on node1
--- mpd TRACE
--- Parallel COMSOL RUN
/home/lubo/comsol/COMSOL40/bin//comsol -nn 4 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log
--- mpd ALLEXIT

--- Job finished at: Wed May 9 11:06:31 CST 2012
------------------------------------------------------------------------------

license logs for step 2
.....
11:01:05 (lmgrd) LMCOMSOL using TCP-port 46447
11:03:00 (LMCOMSOL) TCP_NODELAY NOT enabled
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node5
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node2
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node3
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node1
11:03:08 (LMCOMSOL) OUT: "ACDC" lubo@node5
11:03:08 (LMCOMSOL) OUT: "COMSOL" lubo@node5
11:04:49 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node5
11:04:49 (LMCOMSOL) IN: "ACDC" lubo@node5
11:04:49 (LMCOMSOL) IN: "COMSOL" lubo@node5
11:04:49 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node1
11:04:49 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node3
11:04:50 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node2

comsol bach output for step 1

*******************************************
********COMSOL progress output file********
*******************************************
Wed May 09 10:58:25 CST 2012
---------- Current Progress: 100 %
Memory: 348/348 1048/1048
Current Progress: 0 %
Memory: 370/370 1065/1065
---------- Current Progress: 100 %
Memory: 387/387 1082/1082
Current Progress: 0 %
Memory: 527/527 1359/1359
Linear solver
Number of degrees of freedom solved for: 1484195
- Current Progress: 10 %
Memory: 526/527 1379/1379
- Current Progress: 13 %
Memory: 932/932 1885/1885
- Current Progress: 15 %
Memory: 1125/1125 2057/2057
-- Current Progress: 27 %
Memory: 1068/1125 2003/2057
--- Current Progress: 30 %
Memory: 876/1125 1812/2057
Symmetric matrices found.
--- Current Progress: 31 %
Memory: 1230/1230 2958/2958
--- Current Progress: 32 %
Memory: 1254/1254 2958/2958
--- Current Progress: 33 %
Memory: 1279/1279 2958/2958
--- Current Progress: 34 %
Memory: 1298/1298 2958/2958
--- Current Progress: 36 %
Memory: 1318/1318 2958/2958
--- Current Progress: 37 %
Memory: 1359/1359 2958/2958
--- Current Progress: 38 %
Memory: 1383/1383 2958/2958
--- Current Progress: 39 %
Memory: 1399/1399 2958/2958
---- Current Progress: 40 %
Memory: 1421/1421 2958/2958
---- Current Progress: 41 %
Memory: 1448/1448 2958/2958
---- Current Progress: 42 %
Memory: 1460/1460 2958/2958
---- Current Progress: 43 %
Memory: 1481/1481 2958/2958
---- Current Progress: 46 %
Memory: 1497/1497 2958/2958
---- Current Progress: 48 %
Memory: 1514/1514 2958/2958
----- Current Progress: 50 %
Memory: 1533/1533 2958/2958
----- Current Progress: 52 %
Memory: 1549/1549 2958/2958
----- Current Progress: 54 %
Memory: 1562/1562 2958/2958
----- Current Progress: 56 %
Memory: 1580/1580 2958/2958
----- Current Progress: 59 %
Memory: 1597/1597 2958/2958
------ Current Progress: 60 %
Memory: 1622/1622 2958/2958
------ Current Progress: 62 %
Memory: 1628/1628 2958/2958
------ Current Progress: 64 %
Memory: 1647/1647 2958/2958
------ Current Progress: 67 %
Memory: 1662/1662 2958/2958
------ Current Progress: 68 %
Memory: 1682/1682 2958/2958
------- Current Progress: 70 %
Memory: 1693/1693 2958/2958
------- Current Progress: 73 %
Memory: 1710/1710 2958/2958
------- Current Progress: 75 %
Memory: 1726/1726 2958/2958
------- Current Progress: 77 %
Memory: 1753/1753 2958/2958
------- Current Progress: 78 %
Memory: 1762/1762 2958/2958
-------- Current Progress: 81 %
Memory: 1777/1777 2958/2958
-------- Current Progress: 83 %
Memory: 1796/1796 2958/2958
-------- Current Progress: 85 %
Memory: 1811/1811 2958/2958
-------- Current Progress: 87 %
Memory: 1828/1828 2958/2958
--------- Current Progress: 90 %
Memory: 1844/1844 2958/2958
Iter Damping Stepsize #Res #Jac #Sol
---------- Current Progress: 100 %
Memory: 2161/2161 3284/3284
1 1.0000000 0.53 1 1 1
Total time: 91.721 s.

comsol batch output for step 2

*******************************************
********COMSOL progress output file********
*******************************************
Wed May 09 11:04:41 CST 2012
---------- Current Progress: 100 %
Memory: 361/361 1061/1061
Current Progress: 0 %
Memory: 383/383 1082/1082
---------- Current Progress: 100 %
Memory: 395/395 1091/1091
Current Progress: 0 %
Memory: 543/543 1375/1375
Linear solver
Number of degrees of freedom solved for: 1484195
- Current Progress: 10 %
Memory: 657/657 1592/1592
- Current Progress: 13 %
Memory: 1269/1269 2365/2365
-- Current Progress: 20 %
Memory: 1122/1269 2057/2365
-- Current Progress: 27 %
Memory: 1079/1269 2016/2365
--- Current Progress: 30 %
Memory: 904/1269 1842/2365
Symmetric matrices found.
--- Current Progress: 31 %
Memory: 1141/1269 2391/2391
--- Current Progress: 33 %
Memory: 1158/1269 2391/2391
--- Current Progress: 35 %
Memory: 1178/1269 2391/2391
--- Current Progress: 37 %
Memory: 1195/1269 2391/2391
--- Current Progress: 39 %
Memory: 1216/1269 2391/2391
---- Current Progress: 41 %
Memory: 1227/1269 2391/2391
---- Current Progress: 43 %
Memory: 1244/1269 2391/2391
---- Current Progress: 45 %
Memory: 1261/1269 2391/2391
---- Current Progress: 47 %
Memory: 1283/1283 2391/2391
---- Current Progress: 49 %
Memory: 1305/1305 2391/2391
----- Current Progress: 52 %
Memory: 1321/1321 2391/2391
----- Current Progress: 54 %
Memory: 1338/1338 2391/2391
----- Current Progress: 55 %
Memory: 1363/1363 2391/2391
Iter Damping Stepsize #Res #Jac #Sol
--------- Current Progress: 94 %
Memory: 1318/1363 2545/2545
1 1.0000000 0.53 1 1 1
---------- Current Progress: 100 %
Memory: 1853/1853 3262/3262
Node 1:
Linear solver
Number of degrees of freedom solved for: 1484195
Symmetric matrices found.
Iter Damping Stepsize #Res #Jac #Sol
1 1.0000000 0.53 1 1 1
Node 2:
Linear solver
Number of degrees of freedom solved for: 1484195
Symmetric matrices found.
Iter Damping Stepsize #Res #Jac #Sol
1 1.0000000 0.53 1 1 1
Node 3:
Linear solver
Number of degrees of freedom solved for: 1484195
Symmetric matrices found.
Iter Damping Stepsize #Res #Jac #Sol
1 1.0000000 0.53 1 1 1
Total time: 108.638 s.

Temperature Sensor Model

Tue, 08 May 2012 21:11:51 +0000

Hello,

I am designing a temperature sensor using an interdigitated capacitor. Using the electrostatics modules, I was successfully able to design the sensor with the starting capacitance value I wanted. However, regarding changing capacitance with temperature is where I run into problems. Thus far, I have been using the joule heating and thermal expansion module. Can anyone tell me if this is the correct module for my goal?

I have had some measure of success using it. However I find that when I remove the surrounding rectangle with air associated with it in the positive z direction and silicon in the negative z direction, the study completes, but with that rectangle, I get an error of singular matrix/solution does not converge and cannot complete the study. Why is this?

Also, without the surrounding rectangle, and without the proper dielectric in place, it seems that I cannot calculate capacitance correctly, and the values are all very small, approaching zero.

I have attached my model.

I would greatly appreciate help understanding this, thank you.

boundary conditions of applying an alternative current

Mon, 30 Apr 2012 10:07:03 +0000

Hello everyone,

i need to simulate a method which uses AC signal in a relative low frequency of 128 Hz. I have run the simulation of the same device (test Wenner) with DC giving not bad results, but now i need to simulate with AC, as it really is, hoping that it will give similar results to that of DC (since it works in low frequencies). So, i changed my module and i went to AC/DC module, on order to use the module Electric currents of quasi statics, Electrics as you have proposed to me in an earlier question. The thing is that i create points that they have to inject on to a block an alternative current, i.e. sinusoidal. However, when i go to the point boundaries i do not get the option for currents but only potentials.

If instead of the points i create surfaces i go to the surface boundaries and i write an expression for the inward current flow : 0.01sin(8t) for exemple, will it comsol understand automatically the form of the signal or should i also change the solver parameter to time dependent and adjust the time stepping etc? (on the same window i am using the time harmonic currents and not the transient electric currents, is that right?)

Thank you in advance!!!

Marilena

Circuit terminal question

Mon, 09 Apr 2012 01:37:00 +0000

Hi, All,

I'm trying to build a model four terminal nodes. Two of them are COMSOL voltage (terminal 1) and ground (terminal 0), another two is connected to 'external' resistor which is not defined as part of the multiphysics model.

Should I name the two terminal as type 'circuit', and name them 2,3? Then choose the nodes in electric circuit (cir) to be 2 and 3? What else should I do? I'm have an error says The DAE is structurally inconsistent .

Thanks!

surface charge accumulation

Thu, 15 Dec 2011 09:47:47 +0000

Dear all!

I just took a chance on combining electrostatic and transport of charged diluted species. Now I want to account for any accumulated surface charges due to diffusion of the charged species to the non conducting walls.

I tested with “Surface Charge Density” and with “External Surface Charge Accumulation” boundary conditions in conjunction with the concentration c on “No Flux” and “Outflow” boundary. Anyway the results are from my point of view are not reasonable, mostly because I’m expecting the surface charge only to rise up. But with any combination there are also conditions were the once accumulated surface charges experiencing also decay.

Any hints what combination of boundary condition my work out?

Thanks for your suggestions!

Bert

How to define a surface charge that depends on electrostatic potential (stationary solver)

Fri, 21 Oct 2011 17:08:23 +0000

Hi There,

I am using COMSOL 4.2 and I have a 1D electrostatic model. At one boundary, I have a simple fixed potential boundary condition, which is no problem to implement. At the other boundary, I would like to define a surface charge density that depends on the potential at that same boundary. For example, it would be similar to the following equation: Q[C/m^2] = Q_0*exp(-phi/E_A). I would then like the solver to calculate the appropriate value of phi (electric potential) at the boundary and elsewhere in the model, based on the constraint between phi and the surface charge defined at the boundary (which depends on phi).

Does anyone know how I can do this? It seems there should be an easy, straightforward way to define a self-referencing boundary condition.

Thanks in advance,

George

voltage induction due to changing magnetic field

Tue, 24 May 2011 12:14:58 +0000

hello,

I'm a relative newbie to comsol. what I'm trying to do is (I think) relatively easy, but I have no idea how to tackle it. what I need to do is model voltage induction in a coil due to a changing magnetic field. I know how to how to create a coil in a fixed magnetic field, but I don't know how to set up time varying field. but, more importantly, I don't know how to measure the induced voltage. should the coil be open and then specify two points where the voltage would be measured? thanks for any suggestions.

r.

Number of degrees of freedom solved for: 0.

Wed, 23 Mar 2011 14:33:12 +0000

Hello all,

When I try to use 4.0, I met with this problem when solving.

Does anyone know how to fix this? I think it might be that I did not add the mesh to the solver, which is different from 3.5a.

Thank you.