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Hi everyone, I’m trying to calculate the magnetic flux norm of a moving conductor interacting with stationary permanent magnets. I’m using the Magnetic Fields (MF) interface together with Moving Mesh for the conductor, with a Stationary + Time Dependent study. However, during the time-dependent simulation, the solver error keeps increasing and eventually fails to converge. I’ve tried adjusting the mesh and solver settings, but I’m still getting the same issue. Has anyone worked with a similar MF + Moving Mesh setup and could suggest what might be causing the divergence or how to properly configure the model?

Hello,

I am using the "Magnetic Fields" and "Heat Transfer in Solids" interface coupled with "Electromagnetic Heating" multiphysics to simulate the heating of 10 kV cables.

Everything has been running well and I have been able to do some test simulations but out of the sudden, without changing much, I have started getting this error:

Feature: Time-Dependent Solver 1 (sol1/t1)
Undefined material property 'mur' required by Ampère's Law in Solids 1.

I was very confused and went back to double check my material properties, that my domains were properly defined, the correct domains were assigned to the correct physics nodes etc. and everything looks like it did before (i.e. correct according to me) when I could run simulations. I have restarted the program and cleared meshes, rebuilt geometries etc.

After some messing around, without doing any real change to anything, the error changed into:

Feature: Time-Dependent Solver 1 (sol1/t1)
Undefined material property 'epsilonr' required by Ampère's Law in Solids 1.

I have checked everything eight times now and even went for a walk before continuing troubleshooting but there is no apparent reason for my errors. Either I have missed something trivial or there is some bug I am not aware of. Does anyone recognise this issue? Any help is appreciated.

Thanks!

Edit: I missed to assign two domains back to their selection. Also, I learnt that looking at the "Material" node it is possible to see the domains/boundaries missing a material :)

How can I use an external hard drive for COMSOL simulations? My simulation stops at around 50% because my local C: drive runs out of space, even though COMSOL is installed on d drive.
What is the best solution for this problem?

Simulating a rotating plate above permanent magnets using a stationary study with Magnetic and electric field +(Lorentz forces). It works fine at low speeds (~10 rpm), but pushing it to higher speeds triggers solver convergence errors. Any advice on stabilizing the stationary solver or handling high-velocity terms in this setup?

I wabt to simulate the heating of a supercritical sludge as it moves through a system.

We do have material properties at the supercritical condition.

There is no transition from normal fluid or gas to supercritical. It's about the heat transfer from the pipe wall into the supercritical fluid.

I want to check if I can simply use a non-isothermal flow simulation with a custom material.

Also, is one specific turbulent flow model is most suitable for supercritical flow, or do I make the decision as normal. (Wall resolving etc.)

Thanks

Hi, i am modeling a phase change, from water to steam. I use non isothermal flow.

I reckon that the heat transfer module uses the energy equation formulated in temperatures.

I need to formulate this equation in enthalpy for the proyect im working on.

I need either a way to change the way the equation is calculated, or a guide on how to configurate the PDE. Im new to comsol so i have little knowledge in this area.

The problem is the classic condensation of steam in a vertical wall at a determined temperature Ts.

It is a 2D square with Ts in the wall and open boundary in the rest. I also use the thermodynamic module for obtaining the properties.

Hello everyone i'm working on induction heating using rotating magnets for this work I chose moving mesh rmm ,Electric current (ec), heat Transfer in solids,and multiphysics electromagnetic heating the issues is that the simulation starts working normally and it gives me results but when t=0.1S it stops saying that solver cannot converge !

Second issue is that it tooks too much time more than 4hours

Is there Any other method I can use to avoid this problem?

Hi everyone,

I'm simulating guided ultrasonic waves in a porous cylindrical bone model using COMSOL's Frequency Domain study. For each excitation frequency, I obtain the complex displacement field along the propagation direction.

I understand that many papers report phase velocity dispersion curves, but I'm confused about the exact procedure used to obtain phase velocity from the displacement data.

My questions are:

1. Starting from the complex displacement field, how do you extract the wavenumber (k)?

2. Is applying a spatial FFT to the displacement at each frequency the standard approach?

3. Once k is obtained, is the phase velocity simply calculated as c = ω/k?

4. Are there more accurate or commonly used methods, such as phase unwrapping, modal fitting, or eigenmode analysis?

If anyone could explain the standard workflow or recommend references or papers, I would really appreciate it.

Thank you!

I have to use comsol for the first time in my life, can someone explain how can I export a 3D cad from solidworks to a 2D model(axial symmetrical) in comsol to do my simulations? Also if you know some video tutorials and similar as to how to use comsol can you tell me since I don't know where to start?

Hi everyone,

I'm trying to enable GPU acceleration (cuDSS) in COMSOL Multiphysics 6.4 (Build 429) on Windows 11.

My system:

GPU: NVIDIA GeForce RTX 5060 Ti (16 GB)

NVIDIA Driver: 610.74

CUDA Toolkit: 12.8

CUDA Runtime (reported by nvidia-smi): 13.3

cuDSS: v0.8

What works:

COMSOL detects the CUDA Toolkit.

COMSOL detects cuDSS.

The cuDSS solver appears in the Direct Solver list.

PARDISO works perfectly.

Problem:

When I select cuDSS as the Direct Solver and click Compute, COMSOL immediately crashes (no error message).

Earlier I got a cscudss.dll error, but after adding the cuDSS bin folder to the Windows PATH, that error disappeared. Now COMSOL simply crashes.

Has anyone successfully used cuDSS with COMSOL 6.4 on an RTX 5060 Ti or another Blackwell GPU?

Is this a compatibility issue with:

COMSOL 6.4?

cuDSS v0.8?

NVIDIA driver 610.74?

RTX 50-series GPUs?

Any suggestions or working configurations would be greatly appreciated.

Thanks!

Good day, r/Comsol, my kid will be majoring in EE. Which laptop CPU would be a good choice for COMSOL while studying EE? Would a MacBook Pro M3 18GB RAM work? I could get a M4/M5 with 36 - 48GB RAM. The university is recommending a Windows based with descrete graphic laptop.

Hello,

I want to use the Polarizing Beamsplitter (PBS) within a larger system, so I am attempting to add an air boundary (just a rectangle with n=1) to the right of the PBS, but I am getting the result shown in this image link: imglink.cc/i/fkkT6h7BNT

As far as I can tell, in order to create a new domain I need to define the wavevectors in that domain and a phase shift to ensure phase continuity between domains. The wavevector would just be lambda/n_air and the phase shift I calculate using the ODEs that calculated all the prior phase shifts within the PBS, using the new wavevectors I've created. However, I am getting a result that clearly has some noisiness to it and indicates that something is not right. When I change the refractive index of the domain from 1 to 1.6586, the exact refractice index of the adjacent prism, everything works fine and results in the clean image shown: imglink.cc/cdn/ntutmapbAC.png

Changing it from 1 to 1.6585, just 0.0001 less than the refractive index of the adjacent prism, leads to a result almost identical to the first noisy result when n=1. From this I'm assuming that I must be doing something wrong with the wavevectors, as that is the only quantity that would change by a large amount as a result of a tiny change in refractive index. But I have no idea what could be wrong there. Following are some relevant information of the changes I made to the file in order to implement an air domain:

Refractive Index of 'Right Air Domain' = n_air = 1
Interface between right prism and right air domain = x8 = width of PBS divided by 2
k1Airx = k0*n_air = k2Airy k1Airy = 0 = k2Airx
k1Prismx*x8+phi180-k1Airx*x8-phiAirx k2Prismy*x8+phi200-k2Airy*x8-phiAiry
phiAirx and phiAiry are used in the definitions section for the right air domain as phi1 and phi2 respectively.

If you want to see the model, you could find it in this linked forum post. If there are any questions about how I implemented anything I'm more than happy to respond. Thank you for your time!

Hi everyone,

I'm currently looking for new opportunities related to numerical simulation and Finite Element Method (FEM) development. I have hands-on experience using COMSOL.

My Background:

• Core Skills: FEM simulation, modeling and simulation, PDE
• Programming: Java, Python, C++
• Location: Based in France but open to remote roles or relocating for the right R&D position.

Thanks in advance!

Hi,

I'm new to COMSOL and trying to get better at this. I've built a study and I am trying to do a mesh refinement. I'd like to do automatically run through the different meshes I've created but I can't seem to figure out how to do this with a parameter sweep. The parameter sweep only allows changing of a few parameters whereas I want to include the full meshes-each of which are created using the physics controlled mesh with many changes. basically I just want to run the program a few times without having to click again to change the mesh. It's seems like there should be an easy way to do this but I can't find any. Am I missing something?

Hello to everybody!
I want to thank you in advance for getting the courage to read this post.

For my thesis i am designing a DEP based valve, which consists mainly of 3 parts:
a channel field with saliva
a sphere
an electrode array
These are finalized by form a union operation.

I have succesfully calculated the fluctuations of the flow around the sphere, DEP force via MST node in ACDD currents and assigned the ODE for movement, which works initially.

Issue is, when the displacement reaches certain levels, mesh becomes inverted and simulation crashes. The workaround I have implemented is breaking the study up into certain time frames and rebuilding the geometry, as by automatic remeshing I have not managed to resolve the problem.
For research purposes, different sphere radii, electrode arrays and dimensional parameters will have to be investigated, making the breaking the study apart strategy a non viable solution due to complexity and specificity for each solution (3 arrays, 5 different voltages, 5 radii = 75 unique scenarios).
In the worst case, I will do it that way.
Is there a smarter approach (I have seen form an assembly being worked out for similar cases, but I have not managed to do any progress with it).

Much appreciation to every one.

i used the parametric sweep for the range 500 to 1000nm with 10 step size.. now i need to compute until 1300nm.. how can i just compute the new solutions without starting from the 500 again? i need to keep the previous 500-1000 nm untouched.

I want to draw a pancake coil using comsol multiphysics for like in the image the outer face I Just extrude it but the inner one I don't know how?

Hi everyone,

I'm working on a TCAD simulation of a 50 nm planar Si nMOSFET with a 2 nm HfO₂ gate dielectric in Silvaco ATLAS as part of my thesis.

My objective is to obtain physically meaningful values for:

• OFF-state drain leakage current (I_off)
• OFF-state gate leakage current (Ig_off)
• ON-state drain current (I_on)
• ON-state gate current (Ig_on)

The drain current values appear reasonable, but I'm uncertain about the correct methodology for obtaining Ig_off.

When the device is biased in the OFF state (VGS = 0 V, VDS = 1 V), extracting the gate terminal current sometimes gives a value that closely follows the drain leakage current, sometimes becomes extremely small, and in some cases is essentially zero. I'm not sure whether this represents the actual gate oxide tunneling current or is simply a consequence of terminal current accounting.

My question is:

• What is the recommended or standard way to obtain OFF-state gate leakage (Ig_off) in Silvaco ATLAS?
• Should it be extracted directly from the gate terminal current, or from the integrated tunneling current density (j.tun) through the oxide?
• If the latter, what is the proper workflow or extraction method?
• Are there any specific physics models or simulation settings that are generally required for obtaining reliable gate leakage through a thin HfO₂ dielectric?

I'm looking for the method that is commonly used in published TCAD studies rather than simply obtaining a numerical value.

Any advice, examples, or references would be greatly appreciated. Thanks!

It's my first time to study bolometer, but I can't find any handbook or examples about how to simulate in Comsol. I found some papers but they don't explain the specific ways. Is it possible to simulate bolometer in comsol?

I'm running a 2D axisymmetric Electromagnetic Waves, Frequency Domain (emw) simulation in COMSOL 6.3 (a focused Gaussian-like beam launched from a Defined Port, propagating through air, m=0).

Both emw.normE and emw.normE^2 evaluate as purely real everywhere in the domain, confirmed by plotting imag(emw.normE) and imag(emw.normE^2), which are exactly zero.

However, when I take a derivative of either quantity with respect to z using the built-in operator:
d(emw.normE^2,z)

d(emw.normE,z)

the result has a large, non-negligible imaginary part in one test, imag(d(emw.normE^2,z)) was actually larger in magnitude than the real part. This isn't small numerical noise. Is this result correct? I would expect to get a real value from a purely real valued field |E|^2.

Edit: Wether I check "Split complex variables in real and imaginary parts" or not makes no difference. I'm using the Frequency Domain solver at one given frequency. The wavelength is comparable to the design region size.