Latest Discussions - COMSOL Forums

Difference between MF and MEF

Thu, 21 Nov 2024 11:58:45 +0000

What are the differences between MF and MEF module. Can MF module be used for Lorentz force calculation where the AC current frequency is 500 Hz. Also can eddy currents be found using MF module. If not where to use MF and MEF module.

How to Create LED model with the Optics module?

Thu, 21 Nov 2024 09:31:49 +0000

hello,

I am making an LED model with an optical module. I want to get an optical result of how much light is transmitted from the light emitting layer (Alq3), but it is difficult to check the transmittance with the current port setup.

Can you tell me how I can set up the physics to emit light to the anode and cathode at the same time and see the transmittance?

Thanks!

Sellmeier equation for silicon

Thu, 21 Nov 2024 09:04:04 +0000

Hello,

I wanted to simulate a silicon waveguide with silicon air bilayer for modulation. In that simulation I wanted to put the ng of silicon as 4 and I wanted to put the Sellmeier equation for silicon also. where will put those in COMSOL.

Parametric Sweep Interpolation Results

Wed, 20 Nov 2024 16:59:00 +0000

Hello,

I have run a tensile test parametric sweep where the sample is strained to 80% nominal strain at a rate of 10% strain per second in a time-dependent calculation. I would like to create a plot showing the strain at which each curve crosses the 5 kPa stress mark.

I believe this might involve using an interpolation function, but I am unsure about the exact syntax or setup. When I run a boundary probe for stress, the output table contains columns for modulus (μ), time, and stress. I am not sure how to extract the specific strain values corresponding to the 5 kPa stress from this table for each corresponding modulus sweep.

Would a parametric curve approach work better, or is there a way to process the probe results directly to get what I need?

Attached is the result from my simulation.

Richardson Equation

Wed, 20 Nov 2024 14:19:24 +0000

Hi Everyone,

I am quite new towards COMSOL Multiphysics.. I am current conducting a simple research on groundwater flow. Does anyone knows the definition of aquifer thickness in a 2D simulation. In addition to that, how do I define the thickness of a 2D domain?

I sincerely seek for some guidance in this matter.

Answers are very much appreciated.

Heat transfer in actively-cooled composite

Wed, 20 Nov 2024 13:27:20 +0000

I have set up a heat transfer in solids and fluids model to mimic an experiment and I am having trouble getting accurate temperature results.

In my experiment, I have a composite sample with three hollow channels embedded within it. I heat the bottom surface of the sample with a heater mat which is controlled by power input. I then actively cool the sample by pumping water through the channels. I capture the before and after surface temperatures using an IR camera.

My model has been set up in the same way. I have a boundary heat source at the sample/heater mat interface and surface-to-ambient radiation on all other surfaces. In the flow case (10-30ml/min) I have maximum and average temperatures in good agreement with my experimental results at the same heating rate (within 10%). However, in the no-flow case, the temperature in my model is 240% higher than my experiment (exp ~ 50 degrees at 3W; model ~ 120 degrees at 3W). Does anyone know the reason for this large discrepancy?

I have tried changing the heat source from domain to boundary and from heat rate to heat flux. I have also tried modelling open surfaces as external free convection or with convection coefficient instead of surface-to-ambient radiation. Whatever I try seems to give a similarly high spike in the results.

COMSOL Multiphysics® Version 6.3 is now available!

Tue, 19 Nov 2024 19:22:26 +0000

We're pleased to announce the release of COMSOL Multiphysics^® version 6.3.

Highlights include:

Electric Discharge Module: a new product that can be used to simulate electric discharge and breakdown in gases, liquids, and solids, for applications such as high-voltage system components and consumer electronics
GPU-based acceleration in support of acoustics simulations and surrogate model training
An interactive Java environment for model modification
An optional Chatbot window for programming and debugging assistance
New automated geometry tools for robust meshing

See the complete list of new features and download version 6.3 here: https://www.comsol.com/release/6.3

How to model a square wave transient current in AC/DC module

Tue, 19 Nov 2024 12:22:13 +0000

I have used the rectangle function in comsol and defined the shape of one pulse. How can I make this a series of pulses when the frequency of my current is 500 Hz.

Thank you

regarding the performance analysis of TFT (thin film transistor)

Tue, 19 Nov 2024 10:53:44 +0000

Dear sir, I have simulated one TFT model. For that in small signal analysis I want to make 1. frequency as a independent variable (on X-axis) and 2. oxide thickness as a independent variable (on X-axis) But it is showing some errors while normal ac as well as dc studies are working.Please share some file from where I can get help to resolve my problem.

Questions for combining Mode Analysis with DC Bias

Tue, 19 Nov 2024 02:42:03 +0000

Hello,

I would like to simulate some electro-optic effects in rib waveguide structures: namely I would like to see how mode analysis will vary at a 10-Volts bias voltages. I've combined the electrostatic physics interface with the eigenwave-frequency-domain interface. Though the mode analysis is simulated properly, I'm not sure if the electrostatic field/potential calculations are actually executed:

Under the Results->ElectroStatics tab, the field profile seems not making sense, as the electric field intensity between the two biasing electrodes are almost zero. The potential across the electrodes is also not varying at different spatial points.

I wonder if there is any way I could trouble shoot the process? Thank you!

Plotting Electric Field in RF Module

Tue, 19 Nov 2024 02:06:20 +0000

Hello,

I am trying to plot the electric field of a nanowire using COMSOL 5.3a RF module. I have been exploring emw.normE, emw.Ex (Ey,Ez) etc, but I am wondering how to just plot E⇀ rather than norm.E? Furthermore, what is actually being plotted with emw.Ex, it is the real part but is that the full vector magnitude of the X part of the electric field?

Thank you! Clarissa

Diversity of acoustic streaming in a rectangular acoustofluidic field

Mon, 18 Nov 2024 20:00:43 +0000

Hello everyone, I'm trying to do the following simulation of the following article: https://doi.org/10.1016/j.ultras.2014.11.015. The acoustic pressure of my result is not in agreement with the reference result, can someone who has already redone this simulation help me? Kind regards.

Simulation: https://drive.google.com/file/d/1RaecszjvZnRhVspwHF408IPBSorbOk63/view?usp=sharing

Magneto mechanics coupling

Mon, 18 Nov 2024 16:32:28 +0000

Hi, I'm a new COMSOL user and I'm trying to model the deformation of a magnetized polymer due to an external magnetic field. The problem that I'm facing right now is that in the structural mechanics - magnetic fields, no currents coupling there aren't any domains where the coupling is applicable. My model is quite simple, it just consists of two rectangles (2D), where the outer one is the air domain and the inner one is the polymer, but I can't get why the coupling is not applicable to the polymer. To me it seems that the coupling is not possible because the polymer is magnetized (using "Magnetic Flux Conservation" node). I attach a screenshot of my model builder if it can be of any help.

Thank you in advance if you can help me!

Stop an eigenfrequency problem, and resume later

Mon, 18 Nov 2024 14:49:24 +0000

Hello

I want to know if there is the possibility to stop an eigenvalue problem and be able to resume it after that. I am running an eigenvalue problem in Pressure Acoustic module. I dont see any "Stop" button in the "Progress" tab.

For a frequency response study I could stop the simulation in the middle of the run using the "Stop" button and observe the already calculated results. However I didnt resume the simulation.

Including Magnet In frequency Analysis of Cantiliver

Sat, 16 Nov 2024 07:26:16 +0000

Hello, Im a newbie into COMSOL , i was trying to attach a magnet as proof mass on a cantiliver and then keep another magnet at rest position with a small distance separating them, with same polarity facing each other .

Now i would like to see: 1) the displacement of the tipmass(magnet on cantilever) considering the force of repulsion at a given frequency , say 40 Hz , which user can give as input. 2)If possible i would also like to see the change in natural frequency on the cantilever due to the force of interaction. When i try to implement , a warning is popping up : Magnet remanence i not considered in frequency domain analysis. Ive added solid mechanics and Magnetic Field (mf) as physics . Stationary and frequency Domain as studies to simulate Is there any solution to solve 1) and 2) or atleast either of them? Any idea/suggestions would be of great help. Thanks in advance!

Undefined material property 'epsilonr' required by Current Conservation 1

Fri, 15 Nov 2024 20:49:02 +0000

I have written code that generates geometry and assigns materials to all of the geometry I am working with but every time that I execute the code and then press the compute button in my app I keep getting an error that 'epsilonr' is not defined. I have tried specifying the values for each material within the code and that hasn't worked either. I have attached the file I am working on.

Optimizing Harmonic Response Analysis for AIV in a Complex Pipeline Using Aeroacoustics-Structural Simulation Methods

Fri, 15 Nov 2024 06:28:23 +0000

I am researching the harmonic response of AIV (Acoustic-Induced Vibration) phenomena with Aero Vibro-acoustics within a pipeline. The goal is to analyze the harmonic response of the pipeline caused by vibrations from the acoustic sources generated by aeroacoustics. However, the pipeline I’m examining is 21 meters long, with conditions involving two inlet branches and one outlet branch, with all three branches parallel to each other and connected by a main horizontal pipe segment. Do you have any suggestions for optimizing this?

I then explored a second method: conducting broadband noise analysis with a much faster steady-state CFD simulation. My idea is to manually translate the sound source distribution from the aeroacoustic simulation mapping and convert it into quadrupole point sources in the acoustic-structural module. Is this second approach feasible, and if so, what would be a valid way to perform this conversion?

Trouble with Magnetic Field Simulation Assembly

Thu, 14 Nov 2024 22:19:15 +0000

I'm trying to run a magnetic fields simulation on a model that i created in solidworks, yet im having some trouble getting it to run:

I started by importing my Solidworks model into COMSOL 6.2.0.415 using the import feature in the Geometry tab. I made an assembly in Solidworks and exported the assembly as a solidpart file (because COMSOL gave me source file errors when trying to import the assembly). I have the length unit selected as "From CAD document", and "solids" checked under the section "Objects to import".

After importing my file, I rotated it 45 degrees, placed a repair node in (from right clicking on Geometry -> Defeaturing and Repair -> Repair), and placed a block around the model (to simulate air around the model). I started with Form Union, but when I rendered my mesh, it gave me multiple errors because the Solidworks model is too complicated, so I proceeded to use Form Assembly. In the form assembly tab, I have "create pairs" selected, and the pair type as "identity pair".

Moving down to the magnetic fields interface, I noticed that when placing the node in, free space, magnetic insulation, and initial values are all defaults. Moreover, the magnetic insulation component selects every face inside the box (which is meant to be a magnetically permeable material) and the box itself (which is air). I add in Ampere's Law in Solid's to select the parts inside of the box that are supposed to conduct magnetic fields with the selection "Magnetization" highlighted with a given material magnetization, but when I run my simulation, I run into an issue where the flux is near zero (on the order of E-16 teslas) which makes sense because the tangential component of the fields on the parts of the model that are supposed to conduct magnetic fields are forced to zero; given Gauss' Law for magnetic fields the magnetic field should be zero. Therefore, the fields don't permeate outside of the model.

Given that analysis, what I want to do is have COMSOL assume only the box (air) to have the boundary condition of magnetic insulation, and all the parts of the model inside the box to show up as either (overridden) or (not applicable) in the Domain Selection tab, to where I would naturally select Ampere's Law for Solid's (this would normally work assuming that I would select Form Union in the Geometry tab, because COMSOL merges the boundaries between components in an assembly).

I looked online and used a few resources and I found that creating a continuity boundary between parts of the assembly sets a constraint where the boundary conditions on the outside of the box define everything inside of it; in other words creating a continuity boundary manually forces the boundaries on the outside of the box to be magnetic insulation and everything else inside is free to be assumed with Ampere's Law for Solid's. I read online that this is automatically done with Form Union, and Form Assembly needs this to be done manually.

Given that, I went and checked under "Definitions" to see the Identity Boundary Pair, and it made pairs between each of the components in the assembly. After running it again (where the Magnetic Insulation is still selecting everything inside the box), I run into the same issue. I then try to implement a Continuity Boundary in the Magnetic Field's interface, and I see that all of the components inside aren't selectable (it says "not applicable"). So i then try to select all components inside of the box and add a Magnetic Field's boundary condition, assuming that COMSOL will recognize that if I keep the initial parameter of the boundary condition of the tangential magnetic field to be zero, it will allow the magnetization to conduct in the material.

I either get an error message that says: Divergence cleaning failed for Auxiliary-Space Maxwell (AMS), or I run into the same issue where the magnetic flux doesn't permeate out of the material inside the box of air, and the magnetic field is still around the value of E-16 Teslas (essentially zero).

I even tried creating my own identity boundary between the model inside the box and the box itself (where I selected everything inside the box as the source, and the destination as the box, as well as vice versa, and it still doesn't work)

What am I doing wrong here? Do I have the correct approach when trying to solve this problem?

I attached a picture of my Model Builder Hierarchies, however, I'm not able to link my COMSOL model due to privacy concerns. Could anyone help me?

Edit: I have one section of my model to be a magnetization-based solution, so i set the magnetization myself, and another section is to be influenced by such magnetization, which i set the magnetic properties to be the material's relative permeability. When i run it as is, I get the AMS error mentioned above. When i set both components to be magnetization, it runs fine but it's not what I'm looking for. I have a hunch its an issue between the boundary conditions. Could anyone help me solve this issue?

Questions for Mode Analysis Boundary Conditions

Thu, 14 Nov 2024 05:12:41 +0000

Hello,

I'm currently using 2D Mode Analysis study to perform some optical mode analysis on a 2D waveguide, consisting of Lithium Niobate (core), SiO2 (substrate and cladding). I realize that if I set all boundaries to be "Scattering boundary conditions", the computed simulation field is very weekly confined in the waveguide region. However, if I change some boundaries to be "Perfectly Electrical Conductors", the field is confined within the waveguide very well. Intuitively the simulation I'm performing should be purely optical without any electrical contacts, which should not be affected by boundary conditions at all. Hence I wonder why the changes of boundary conditions will heavily impact the simulation field profile? Please feel free to let me know if there is anything I set incorrectly.

Guidance for Model Methods

Wed, 13 Nov 2024 16:37:48 +0000

Hello COMSOL community,

I am a PhD student working on nonlinear methods in structural mechanics. I recently discovered that COMSOL offers applications that can be shared, and I am interested in learning how to create a model method to automate my model. If anyone could provide guidance or point me to relevant blog posts or resources on model methods, it would be greatly appreciated.

Thank you!