Latest Discussions - COMSOL Forums

Eddy Simulation as Inspection

Mon, 07 Jul 2025 00:26:23 +0000

Hi, I'm a doctoral student using the License number COMSOL® 6.3, in my thesis. So, my objective is to simulate an eddy current inspection for a heat exchanger tube. You can understand this kind of test by watching the video on the YouTube link (https://youtu.be/MYd92lzhsX8?si=mtOjR_rgwhkP2LJP). How can I assemble this kind of model in COMSOL? Could you please help me? Basically, I need to insert a bobbin coil sensor probe inside a tube, where the probe should be moving inside the tube along time. In the end, I want to see the impedance plan for each step, XL versus XR, and all steps as voltage versus amplitude versus probe displacement. Please, I need your help!!!

Two sided Wall (line) boundary conditions - Form Assembly

Fri, 04 Jul 2025 15:04:19 +0000

Hello, when there is a line which is wall in form assembly, so, there is 2 sides of this wall. Can I use different boundary conditions in this situation? As example: one side is No Slip and the other Slip condition?

I make a simple test and When I did this, It was give different velocities when I compare the side of Slip condition. So, when I use the 2 sides as Slip it give me correct solution. When I use No slip in one side and Slip in another, the Slip condition is giving different value compared the prior test.

Using current dependance in Joule heating module

Fri, 04 Jul 2025 11:43:52 +0000

Hello everyone, I've just started learning how to use COMSOL.

I'm using the Joule Heating module to model a conductor connected to an electric potential on one side and grounded on the other to analyze heat transfer. Everything works perfectly when I use only the electric potential. However, when I try to analyze the heat dependence of the conductor using a constant current (by applying a Terminal condition), nothing changes after computing in terms of temperature.

How can I change the model depends only on the current instead of the voltage? How should I modify the model to reflect this?

Any ideas, suggestions, or advice would be greatly appreciated!**

Boundary Error in meshing

Thu, 03 Jul 2025 21:41:09 +0000

I am modeling a laser cathode stem that uses a heater coil for joule heating.

My issue is that the bottom portion of my coil has 0 spacing between them, the windings are directly on top of each other. When I am meshing in COMSOL the boundaries are giving the error of "intersecting face elements." I have this on "extremely fine" free tetrahedral. I tried ignoring edges and some boundaries but it just seemed to cause more issues that I don't know how to fix.

This is my first COMSOL simulation so apologies if things are a bit unclear. Couldn't seem to reduce file size down even after removing meshing. Added the stp file to show geometry, though.

Requesting Guidance for Vacuum Chamber Analysis – New User Struggling

Thu, 03 Jul 2025 14:44:49 +0000

Hi everyone,

My name is Vijay, and I am currently working on my master’s thesis, focusing on vacuum chamber analysis using COMSOL. I am new to this field and have been struggling to get meaningful results for the past 30 days despite trying my best.

If anyone is available to guide me or provide advice on the workflow, boundary conditions, or setup strategies until I can get my first meaningful results, it would be a huge help. I am open to having a call to discuss my setup in detail if needed.

Simplest CUDA context

Thu, 03 Jul 2025 12:56:44 +0000

Hello!

I have a 1D Weak Form PDE with only one dependent variable u, which has shape-function 'Nodal discontinous Lagrange'. In Compile Equations Statistics it is seeable, that this dependent variable u creates 45 Deegrees of Freedom, and in total there is also 45 Deegrees of Freedom.

But when computing with Hardware Acceleration (CUDA) a warning still says: "GPU calculations disabled. Not all dofs are DG.". But Compile Equations Statistics says otherwise.

How is this possible?

Nice greetings

How can we find the Current distribution on the top and bottom metal surfaces of the absorber

Thu, 03 Jul 2025 11:17:35 +0000

Hi, i am working on metamaterial absorber and i want to know that how can we find Current distribution on the top and bottom metal surfaces of the absorber.

meshing in axisymmetric models

Thu, 03 Jul 2025 09:33:34 +0000

I've noticed that vertical boundaries in axisymmetric models are meshed very coarsely, whereas if I create the same geometry in 3D the equivalent boundaries are meshed more finely.

Is there some explanation for this?

Divergence h(div) as shape-function; which physics interfaces?

Wed, 02 Jul 2025 16:35:09 +0000

Hi!

Which physics interfaces use divergence h(div) as shape functions?

I want solve a 'grad div A' or 'divA*test(divA)' context and want to know how to configure the solver for divergence-shape-function contextes.

Thank you. Nice greetings

Coil turns have the same current ?

Wed, 02 Jul 2025 15:26:24 +0000

Hello,

I am working on a 2D-Axisymetric model, where i am modeling a coil. If i draw each turn individually, spaced, will the different turns have the same current (as they should be connect in series)? If not, and if I am trying to induce current in my coil, how can i ensure this?

Thanks, Vitor

Moving magnets study

Wed, 02 Jul 2025 02:53:22 +0000

I'm new to COMSOL (so new that I just downloaded it yesterday) , and I want to study movements from magnetic forces.

I've been trying to do a 2 magnets study, but I kept getting the " relative error higher than tolerance" error.

Now I've come to seek help from the community.

Error in Coupled Electrostatics-Heat Transfer Simulation: Divergence in Linear Iterations?

Tue, 01 Jul 2025 22:45:23 +0000

Model Description: I am simulating power dissipation in a 3D chip with RF and DC electrodes embedded beneath insulating layers. The simulation uses:

Electrostatics (FEM) coupled with Heat Transfer in Solids.

Stationary study

Applied Voltage: 100 V on the RF electrodes.

Key Assumption: Since the electrode dimensions are in millimeters (mm), I approximated the 20 MHz RF signal as a DC field (quasi-static assumption) and opted for electrostatics instead of full electromagnetics.

Error Message:

Failed to find solution.
In temperature: Divergence of the linear iterations.
Returned solution is not converged.
Not all parameter steps returned.
Note: I kept mesh normal in size. I need the solutions and susggestions asap.

Electric interference

Tue, 01 Jul 2025 08:24:42 +0000

Dear Experts,

I got the following error message:

Parameters: "time","0"
The following feature has encountered a problem:
Feature: Time-Dependent Solver 1 (sol75/t1)
Failed to find consistent initial values.
Last time step is not converged.

The physics: Electric currents
The equation I used: (the polarity changes)
Io*sin(2*pi*f1*t)
- Io*sin(2*pi*f2*t)
Io*sin(2*pi*f1*t)
- Io*sin(2*pi*f2*t)

See at physics.png
Note: though the are two current sinks under the electric current, these are Current source as well. (I know, in Electrochemistry Module there is a designated module to current sink, but I do not have access to it. )

The solutions that did not work: - A Stationary step was added before the Time dependent study
- Using the following equations to avoid the value 0:
- Io*sin(2*pi*f*t)*(1 - exp(-t/tau)) - Io*sin(2*pi*f*t)*(t<ramp_time) + Io*sin(2*pi*f*t)*(t>=ramp_time)

Changing the time range
redo the whole study/physics

Magnetic tumbling robot simulation

Sat, 28 Jun 2025 14:16:24 +0000

Hello, everyone. I wanna achieve a simulation of the tumbling motion of magnetic layer under magnetic field, as shown in the attached figures. Can anyone help me? Thank you very much.

Time-domain Electromagnetic Field Distribution Calculation for Waveguide-Fed Resonant Cavities

Sat, 28 Jun 2025 13:16:32 +0000

Dear experts, I currently need to perform time-domain electromagnetic field calculations for a resonant cavity fed by a waveguide. However, unlike in frequency-domain calculations, I cannot directly apply a rectangular waveguide port excitation. Is there a suitable method to achieve equivalent excitation, so as to obtain results consistent with those of frequency-domain calculations?

Application models for COMSOL 6.0 Version

Fri, 27 Jun 2025 06:54:53 +0000

Good Morning all... Can I get Application models for COMSOL 6.0 version. because currently i am using COMSOL 6.0 version only.

Assistance Required Modeling HV to Signal Wire Coupling

Thu, 26 Jun 2025 13:09:47 +0000

Hello All,

I am attempting to recreate an experiment in COMSOL in which a high voltage wire has an applied switching voltage (300V peak to peak) and is placed within proximity of a test signal wire to observe the coupling between them for EMC/EMI applications. I am however having an issue figuring out which physics interface(s) and domain/boundary conditions I should be incorporating into the model to achieve the expected outcome. The HV wire potential is set to a square waveform and I should be observing spikes in the signal wire potential at the rise and falls. I have played around with ES and EC to no avail and before I start poking around further on my own, I figured some guidance would be a better option to get started

All of my previous COMSOL experience has been with microfluidics reasearch so I'm a little unsure changing things up but any help would be much appreciated!

Bulk acoustic streaming imputing the equations

Thu, 26 Jun 2025 12:28:45 +0000

Hello everyone.

I am trying to reproduce an acoustic streaming simulation using COMSOL version 6.2. With the domain and boundary couplings, I am not able to achieve the results presented in the article: the values I obtain show a difference of up to 10⁻³ orders of magnitude. For this reason, I am trying to manually introduce the equations as the author did. I have used all parameters identical to those of the author. Could anyone with experience in acoustic streaming and manual equation implementation help me? Below are my results and the author’s results. I have run tests using both the thermoviscous acoustics and pressure acoustics modules.!

Equations: https://drive.google.com/file/d/1Pjtt3LQDhihuySxl2Bi06AUSFii_ZOeM/view?usp=sharing

Article: https://drive.google.com/file/d/1Oi59P2okPOBGToxr3XVfNY94yljk7Bo7/view?usp=sharing

Quarter-wave Impedance Transformer

Thu, 26 Jun 2025 05:06:42 +0000

Request for Broadband/Narrowband Quarter-Wave Transformer Model (.mph File)

Dear COMSOL Community, I hope you're doing well. I'm currently working on a project involving quarter-wave impedance transformers and would greatly appreciate your help. I'm looking for a COMSOL .mph file that demonstrates both narrowband (single-section) and broadband (multi-section or tapered) λ/4 transformer designs operating around 2.5 GHz on an FR4 substrate (εᵣ = 4.4, 1.6 mm thick), matching 50 Ω to 100 Ω. If you have an existing model or could share one, it would help me validate my S-parameter results, Smith chart plots, and field distributions. I'd be happy to credit your contribution and share my findings in return. Please let me know if you can assist or point me to relevant resources..

Thank you for your time and expertise! Best regards,

Rotating permanent maget

Wed, 25 Jun 2025 21:45:12 +0000

hi,

I'm trying to rotate permanent magnet mechanically, and observe the distribution of magnetic field due to the rotation.

I'm trying with moving mesh-rotating domain and magnetic fields-magnet. As a result, magnet rotates mechanically, but the magnetic flux density is fixed as a initial state.

I want to know why it works like this.

Thank you,