Latest Discussions - COMSOL Forums

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,

Mu metal magnetic shielding and the transition boundary condition

Wed, 25 Jun 2025 19:38:55 +0000

I am trying to model magnetic shielding with mu metal, and from this comsol seminar https://www.comsol.com/video/modeling-electromagnetic-shielding-in-comsol-multiphysics, I am told to use the transition boundary condition to model this.

My question is, why is this a valid way to model magnetic shielding? Looking at the documentation for the transition boundary condition, there is no mention of magnetic fields.

Thanks

Coil/Magnet Simulation

Wed, 25 Jun 2025 17:28:46 +0000

I am modeling an electro-magnet and comparing the results with some measurements. The results are fairly accurate except as you approach the area close to the boundary between the steel and the air domain.

I am just using a tetrahedral mesh. Is there a particular approach I need to take for this boundary?

grad div A - weak expression?

Wed, 25 Jun 2025 15:53:48 +0000

Hi!

When having 3 dependent vector-components: Ax, Ay, Az. Is

(Axx+Ayy+Azz)*(test(Axx)+test(Ayy)+test(Azz))

the correct weak expression for grad div A?

Or splitted in 3 input-fields:

(Axx+Ayy+Azz)*test(Axx)
(Axx+Ayy+Azz)*test(Ayy)
(Axx+Ayy+Azz)*test(Azz)

Nice greetings

Coulomb gauge in temw (RF - Electromagnetic Waves, Transient)?

Wed, 25 Jun 2025 15:46:06 +0000

The below post is related to an archived discussion (RF-transient governing equation)

Someone could explain why the Comsol considers grad (div A) = 0 in the RF-transient module (also called temw)?

...

Why Comsol considers "grad(div A) = 0" ???

Wondered the same.

Nice greetings

How to Model adhesively bonded Single Lap Joint in COMSOL using Cohesive Zone Modelling?

Wed, 25 Jun 2025 10:26:23 +0000

Dear COMSOL Support Team,

I hope this message finds you well.

My name is Abhi, from Indian Institute of Technology Mandi, Himachal Pradesh, India, we are blessed to be customer of COMSOL Multiphysics. I am currently working on modeling an adhesively bonded single lap joint using COMSOL Multiphysics. I have attempted to implement a Cohesive Zone Model (CZM) based on the Mixed Mode Delamination of Composite tutorial provided by COMSOL. or Should I go for zero thickness element to resolve the problem? or any mathematical formulation required for the Simulation study?

However, I am encountering convergence errors during the simulation. I am validating my model against a published research paper (attached for your reference), and I have also included a screenshot of the specific error I am facing.

Please let me know if more data required,

I would greatly appreciate your guidance in resolving this issue.

Thank you for your support.

Best regards, Abhi

Epoxy Resin Curing Process for Basin-Type Insulators Application ID: 137951

Wed, 25 Jun 2025 09:17:05 +0000

I'm trying to re-create the Epoxy Resin Curing Process for Basin-Type Insulators Application from scratch in COMSOL 6.3, but I get the following error when I try to compute my version:

Undefined variable.
  - Variable: comp1.cr
  - Geometry: geom1
  - Domain: 2
Failed to evaluate Jacobian of expression.
  - Expression: dvol*(R*(pi*(comp1.ht.d*(2*comp1.ht.dflux_materialR))))
Failed to evaluate Jacobian of expression.
  - Expression: (2*(comp1.ht.dflux_materialR*test(comp1.TR)+comp1.ht.dflux_materialZ*test(comp1.TZ))*comp1.ht.d*pi*R)*(dvol)

I've had the original version and my version open side-by-side and have tried to go through to find any differences, but can't find any.

I've added a zipped version of my .mph file.

Any suggestions as to how I might resolve this error would be greatly appreciated.

I'm new to COMSOL and just completed a 2-day training course last week and I'm now trying to decide if COMSOL is the right software for my PhD.

How to create a nanofluid

Tue, 24 Jun 2025 03:48:25 +0000

Greetings! I have a problem to simulate a nanofluid flow over a surface in COMSOL.

How can I create a nanofluid combinations of Water + Al2 O3 (with sizes typically of 1-100 nm) suspended in liquid.

I was wondering what libraries do I need to include in the model and how to get started.

Thanks in advance.

3D PNP model: Time-dependent solver fails to converge (Membrane potential simulation)

Mon, 23 Jun 2025 20:40:25 +0000

Dear COMSOL Community,

I hope you are doing well. I’m currently working on a 3D simulation of membrane potential using a coupled Poisson–Nernst–Planck (PNP) model in COMSOL Multiphysics 6.3.

I would greatly appreciate any advice or suggestions regarding the issue described below. Thank you in advance for your time and support.

I’m trying to simulate the membrane potential using the following physics interfaces:

Electrostatics (ES)
Transport of Diluted Species (TDS)
Multiphysics coupling: Electromigration in Diluted Species

Two ion species (K⁺ and Cl⁻) are defined with appropriate charge numbers, diffusion coefficients, and initial concentrations inside and outside the cell. The membrane is modeled as a dielectric region (TDS excluded), and the outer solution is modeled as a large domain to approximate a reservoir.

The initial values are set as: - V = 0 V - c_K = 150/5 mol/m³ (inside/outside) - c_Cl = 20/120 mol/m³ (inside/outside)

However, the time-dependent solver fails to converge with the following error message:

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

Could anyone kindly suggest: 1. How to diagnose inconsistent initial values in this context? 2. Techniques to stabilize the time-dependent solver in a PNP model? 3. Whether a working 3D PNP example involving ion transport through a membrane is available?

Thank you very much for your help!

COMSOL Not Utilizing CPU – Only Memory. Why? (Lamb Wave Simulation Issue)

Mon, 23 Jun 2025 19:32:22 +0000

Hi everyone,

I’m currently running a Lamb wave simulation in a plate using COMSOL Multiphysics. The original model length was 50 cm, and it used to take roughly 1 day to complete on a system with 32 GB RAM. I recently increased the model size to 550 cm and upgraded my system to 96 GB RAM, expecting improved performance.

However, I’m seeing very slow simulation speeds. The simulation is around 45% complete after more than 10 days, and it seems stuck for the last 4 days. Monitoring system performance via the Windows Task Manager, I noticed:

Memory usage is high, but
CPU usage is almost idle, which is confusing.

It looks like COMSOL is not utilizing the CPU at all, or only minimally, which might explain the delay. Could anyone guide me on:

Why COMSOL is not using the CPU efficiently?
Whether increasing RAM alone helps at this stage?
What other options are available to increase simulation speed? I checked and read about Client-Server mode and parallel computing but don't know more about these.

Attachment size limit does not permit me to attach my .mph file. I am sharing a drive link instead. Thanks.

https://drive.google.com/drive/folders/1UBSIzMQ_S8zAQYrtZTkPg-NehMtbakC2?usp=drive_link

I am struggling with study-2 simulation speed. Would clearing study 1 results and then running study 2 simulation help increase the speed?

Any advice on optimizing hardware or solver settings would be greatly appreciated!

Thanks in advance!

Periodic Boundary Condition in General Form PDE -- No Solution for very Simple Equation

Mon, 23 Jun 2025 15:30:49 +0000

Dear COMSOL community,

I have a lack in understanding solving PDE with PBC, which I can break down to a very simple example, i.e. finding a solution for . The height and width of the 2D simulation domain is , and at the top and bottom a Dirichlet BC () should be applied, while at the left and right site a periodic BC should be applied.

Integrating above equation twice, is given as and from the Dirichlet BC we get and from the periodic BC .

However, when implementing this in the COMSOL general form PDE interface and solving using a Stationary Solver, I do not get the result but an error "Failed to find a solution. The relative error (0.0092) is greater than the relative tolerance.", even not when I use the calculated solution as initial values. However, when replacing the periodic BC at the left and right Interface with a Dirichlet BC , I get the expected result. Therefore, I have two questions:

Why don't I get any result when using periodic BC at the left and right interface?
Why does the periodic BC not overwrite the default Zero Flux 1 BC, but contribute to it? I also implemented what is suggested here, which then overwrites the Zero Flux 1 BC, but I get the same error as using the implemented Periodic Condition.

Attached is a file of the simulation.

Thank you in advance!

How to extract the spot diameter as a scalar?

Mon, 23 Jun 2025 09:52:24 +0000

Hello.

I am currently using COMSOL for research purposes. I want to know how to extract the spot diameter as a scalar obtained in 3D simulation of ray optics or possibly the function which computes it, as I want to pass it to the optimization function of the study. Can someone guide me how to do this?

Ensure mesh has only Tet-10 elements

Sun, 22 Jun 2025 20:41:23 +0000

I have a new app for the Apple Vision Pro that shows FE mesh and FE results in an immersive environment, but only for tet-10 elements. I have figured out how to use LiveLink Matlab to export all tet-10 elements that are created using the "Free Tet" mesher. However, when I display the mesh with the Vision Pro app, it shows a large portion of the mesh, but not all. I believe that's because of the "boundary and edge elements" that are created with the "Free tet" mesher. These are, possibly, triangular and line elements? Can I force the "Free tet" mesher (or another mesher in Comsol) to only generate tet-10 elements?

Simulation of Wire Laser Additive Manufacturing (WLAM)

Sun, 22 Jun 2025 16:27:56 +0000

I am learning about WLAM process simulation including thermal history of the layering process, deformation, stress, shape prediction of the layering layer... Currently, I have been able to create a material model outside the available library, create a laser source model moving in different directions, simulate and get the results. However, I have not been able to perform the layering process (for example: 4-layer deposition). I look forward to receiving everyone's help.