Latest Discussions - COMSOL Forums

Reverse Bias of schottky diode (2D)

Sat, 22 Sep 2018 04:54:42 +0000

I want to know whether any one has succeeded in using COMSOL to simulate the reverse bias of schottky diode or not? My model can only work at forward bias condition. When it comes to the reverse bias case, Error appears. Thanks!

Volume average - multiple evalutions without tedious work

Fri, 21 Sep 2018 23:05:30 +0000

Hello everyone, in my project i would like to obtain average values of magnetic fields over ~100 or so domains in my model. My question is as follows: is there any quick/not extremely tedious ways to obtain 100 evaluations (each evalutionis done in a different domain) into one table or exported file? As unexperienced Comsol user it seems that there must exist a way to do that without obnioxous amount of clicking.

I would be very greatful for suggestions/solutions. Sincerely, Peter

Comsol with MatLab, Execution error

Fri, 21 Sep 2018 21:49:55 +0000

Hi everyone,

I was running a simulation of the .m file of comsol with matlab and I get the following error, I tried to solve it but it was not possible:

No appropriate method, property, or field component for class com.comsol.clientapi.impl.ModelClient.

Error in Interfaz>pushbutton1_Callback (line 136) model.component.create('comp1', false);

COMSOL Multiphysics Plasma Module

Fri, 21 Sep 2018 20:51:14 +0000

hii i am using COMSOL software for modeling 1 D dbd plasma. ........................ i want to add nitrogen and oxygen cross section in my model. as plasma is at atmospheric pressure. comsol only have built in Ar_xsecs.txt file can anyone provide me the txt files of nitrogen and oxygen gas.

warning when importing geometry from autocad 3D

Fri, 21 Sep 2018 16:18:54 +0000

after importing geometry from autocad 3D the messages says there are 15 warning (warnings: face to face inconsistency) how can i deal with that?

Implementing 1D first order PDEs in the weak form

Fri, 21 Sep 2018 13:25:53 +0000

Hi everyone,

I need some help to implement weak form PDEs in comsol.

I'm trying to implement the following system of 1D first order PDEs in the weak form:

with .

In weak form these equations are

So I think that using the "weak form PDE module" I can writte this problem by inserting

-vt*test(phi1) - c1*test(phi1)*Px

-Pt*test(phi2) - c2*test(phi2)*vx

in the "weak form PDE" node and the boundary conditions by using the "dirichlet boundary conditions" node. However, I don't know how to insert the right hand side of the second equation.

For a scalar PDE, tt seems that it can be done by is using the "weak contribution" node at the point of the domain, as I saw in this tutorial. But I don't know how to use the weak contribution node when I have two weak pdes. Anyone know how to help me?

Thanks in advance,

Gustavo

Bio-electronics, Bio-engineering

Fri, 21 Sep 2018 05:25:34 +0000

I am trying to design a magnetic biosensor and I want to perform antibody-antigen reaction on surface for detection. Please help me out and suggest which modules of COMSOL I should use to design this biosensor?

ODEP Simulation

Fri, 21 Sep 2018 03:19:58 +0000

Hello,

I am a newbie to Comsol.  I would like to model the effect of incident light on a photo conductive layer of hydrogenated amorphous silicon.  The a-Si: H layer seperates two conductive and tansparent layers, which have an AC voltage applied accros them.  A small channel exists between the a-Si layer and the top conductive layer, which will house an induced electric field used for experimentation.  The simulation will include the change in the electric field as the conductivity of the a‐Si: H changes.  This is a common procedure in optically induced dielectrophoresis chips. However, I have not found a paper which makes any reference to achieving this simulation in comsol.  Are there any modules which can model the incident light and the change in conductance in the photo conductive layer?  Below should be link to a photo which illistrates the chips design.

Thanks ahead of time.

(https://www.spiedigitallibrary.org/ContentImages/Journals/JBOPFO/19/4/045002/FigureImages/JBO_19_4_045002_f001.png)

simulation to Ionizing air blower

Fri, 21 Sep 2018 02:10:25 +0000

Ionizing air blower is a kind of static equipment for industries which depends on the high-pressure generator to ionize the air and make it become positive and negative ions. Then the air blower will blow the ions to the surface of the object, so that the positive charge will neutralize with the negative charge of object and the charge amount can be removed or reduced. I wang to simulate the Ionizing air blower considering the humidity temperature and the collision and charge transfer between ions, what shou i do? thank you.

Using Application Builder to automate data export

Thu, 20 Sep 2018 20:59:40 +0000

I have a COMSOL simulation in which the solution has been generated and the data I want to export has been setup (what data, filename, etc established in the settings). I have 12 different data sets to export and they take some time to export and I find myself making small changes and need to re-export them so I would like to automate this process. These results have tags "data1", "data2", ..., "data12" in their properties window. I right-clicked on the export object in the model builder menu and copied the code as run which yielded:

model.result().export("data1").run();

So then I wrote up a new method with the following code:

for (int ii=1; ii<12; ii++){ model.result().export(concat("data",toString(ii))).run(); }

Both this code, as well as the first set of code I wrote above, when I click "Test Application", open a blank mph window but do not show any thing else, nor do they write any files to the filenames specified in each data set's settings menu. Can anyone suggest how to automate this process correctly?

Coil Optimization

Thu, 20 Sep 2018 15:22:27 +0000

Hallo, my modell is rectangular coil. Number of turns is 10. The distribution of coil is not equal. The distances of different turns are not identical. I want to use Optimization modell to get best distances for maximal inductance. That is, shape of coil soll be optimized.

The Global Control Variables are distance zwischen turns, d1..... d9,d10 The Global Inequality Constraint is 2(d1+d2+d3+d4+d5+d6+d7+d8+d9)+d10+202*r , because the length and width is fixed. The Global Objective is mf.LCoil_1.

The Problem is, if i use Monte Carlo method i can get many results of distance but the objective values are always unchanged and equal to first objective values. If i use MMA or SPONT methods comsol don't optimise my objective. Which settings can i adjust? Which method is best?

Generic COM API Error

Thu, 20 Sep 2018 14:29:53 +0000

Hi,

I found and adapted a COM based connection to the Comsol server to use with different prog. languages (mainly python). The original author and version is from git ("cmphy"). I can start the server, build the ModelUtil and ComsolUtil COM dispatcher. As soon as I try to connect to the server, I'm getting

APIError: Exception occured: ((0, 'ComsolCom', 'COMSOL API can only run in Excel Add-In.', None, 0, -2146233088)

Any idea of a fix or is this the COMSOL way of saying "no third party, please"?

Calculating the speed of sound in orthotropic material

Thu, 20 Sep 2018 14:07:59 +0000

Hi,

I am trying to simulate the ultrasound from a phased array into a material. The material is orthotropic/anisotropic. We know that speed of sound varies according to direction of propagation in anisotropic materials. But when I check here the speed of sound is constant. How do I vary the speed of sound wrt to the direction. I am using the solid mechanics physics for the whole simulation. This question might be a little stupid but any help would be highly appreciated

Thanks !

Optical transition for solar cell

Thu, 20 Sep 2018 10:56:42 +0000

Hi everyone I am currently trying to simulate solar cell based on Semiconductor-Electromagnetic Waves Coupling . The main node that combines two physic modules is optical transition. However, i dont really understand how it re-calculates permittivity and susceptibility in coupled node. Please help me out if you have ever tried and done it. Thank you

Assembling of matrix takes very long

Thu, 20 Sep 2018 09:23:21 +0000

Hello!

I'm trying to solve a (quite simple) 2D-axissym. model of a fixed bed reactor. I have four species where only three a actually taking part in the exothermic reaction. The chemistry is modeled in re (reaction engineering module) and exported to the 2D-model where I use the following modules: tds (transport diluted species), ht (heat transfer in fluids) and br (Brinkmann-equations).

As far as I can see, I set up the model correctly. But when I want to solve it, it takes hours to assemble the matrix!!!

Is this a normal behaviour? Or where could I start finding the mistake?

Thanks in advance! Till

Cannot create native file C:\Users\jong_\.comsol\v53a\recoveries\MPHRecovery

Thu, 20 Sep 2018 09:17:07 +0000

when I compute the COMSOL, it encounter a problem "Cannot create native file C:\Users\jong_.comsol\v53a\recoveries\MPHRecovery" .This problem for me is a new one, who can help me.

the interface of magnetostrictive

Thu, 20 Sep 2018 09:12:44 +0000

the interface of magnetostrictive is defaultly mf module,could I replace it with mfnc module by changing the variable in it? because the mf module is too difficult to convergence. besides,could you tell me the difference the background magnetic field in mf module and mfnc module. thank you very much!

How to define a boundary condition where temperature is a function of temperature gradient?

Wed, 19 Sep 2018 23:09:14 +0000

Hi, I'm new to Comsol and I'm working on a time dependent model. The temperature distribution along a wall is a function of temperature gradient and also something calculated based on result from previous step. My questions are: 1. Do I use Matlab code to define my boundary condition? How can I extract data of temperature gradient from result of previous step? 2. I need to use some code to calculate something every step. How can I do that in Comsol?

Before I come to Comsol, I tried Ansys Fluent, I can define user-defined-function on both boundary condition and 'Execute at end' section, do we have something like that in Comsol?

Any help will be so much appreciated. Thanks in advance.

Jing

Reaction Engineering Module - Discontinuity in the concentration over time plot

Wed, 19 Sep 2018 18:20:54 +0000

Hello all,

While using the reaction engineering module, I sometimes noticed that there were some discontinuity in the concentration over time plot that were generated from a converged solution. It seems that the discontinuity is due to the presence of the negative values. The curve shows the anticipated trend with the discontinuity. Do you know whether the curve is still acceptable?

Thank you, Woo-Jae

Real metal contacts to semiconductor components in model

Wed, 19 Sep 2018 17:43:42 +0000

Hello,

Let me preface this question by adding that I am a relatively novice user of COMSOL.

I am working on modelling a micron-scale device with both semiconductor and metal components. The goal is a simultanous electrical and thermal model. Hence, it is necessary (as far as I understand) to physically include actual metal contacts in the model--as opposed to using the "metal contact" boundary parameter in the semiconductor module.

For models without any semiconductor components, one can easily solve for thermal/electrical effects using the Heat Transfer in Solids and Electrical Currents/Electrostatics modules. However, the Semiconductor module appears to handle it's own electrical variables interally.

So, I am wondering: Is it possible to couple the Semiconductor and Electric Currents/Electrostatics modules in order to model a device with both semiconductor and metal components?

Thanks in advance, Ara