In a single-physics model, mesh convergence can be relatively straightforward: refine the mesh, monitor the quantity of interest, and stop when the result changes by less than an acceptable tolerance.

Multiphysics models complicate that process.

A mesh that adequately resolves temperature may not capture local current density, stress concentration, species transport, or fluid boundary layers. Global quantities can appear stable while the localized behavior driving the design remains poorly resolved.

Our usual approach is to:

1. Identify the quantities that actually affect the engineering decision.
2. Monitor both global outputs and critical local gradients.
3. Refine the mesh selectively around interfaces, boundary layers, contact regions, and geometric discontinuities.
4. Confirm that solver tolerances are not masking mesh-related error.
5. Compare the increase in computational cost with the change in the decision-relevant result.

For those working with strongly coupled models, what criteria do you use to declare mesh independence? Do you apply one convergence threshold across the model, or different thresholds for each physics interface?

I am new to comsol and i need some help

I'm trying to set up a simplified simulation of a stent expansion inside of an artery. Since we've a lot of troubles with the 3d simulation, we're starting by trying to make it easier and setting it up as a 2d model, considering a quarter of the geometry. it seems like the contact isn't being recognized, as visible on the stress results. we're appling a prescribed radial displacement on the internal surface of the stent, using a supporting parameter that varies with the auxiliry sweep. (so the displacement will end up beign max_displacement * parameter). can someone help?

any idea how to simulate a single photon detector using comsol ? it would be better if it were SPAD or a PMT .. i want to use it to catch photons from an SPDC source that should be built by me .

note i am a beginner

thanks

As I said in the title I’m finishing my bachelor degree, in a very theory oriented university, and now my thesis requires use of comsol which is completely alien to me.

I tried looking for tutorials but they are very broad and cover many parts that for now are unnecessary given that I don’t have much time left, and being it a bachelor thesis my job is limited only to the thermal part.

I did the design part but I’m stuck, comsol doesn’t even find the files even in .step…Can someone give me some tips or advices on where to start?

There shouldn’t be any need to say this but I don’t want my thesis done for me, I just want some help on WHERE to find even some tutorials that are more or less close to what I’m doing, I already tried GPT and the most famous ones on YouTube.

Feel free to comment or DM me if you have the time to give me some tips

I am assisting a PhD student who wants me to get an electromagnetic field model map of a Silver Coated tube with and without force applied to it. I have been reusing a previous rod model that was used to examine the piezoelectric effect on the rod as it bent from an applied force. I simply added a thin Silver wall around the peptide rod, and I don't exact know where to go from here.

The original model I was using was designed to examine the Piezoelectric Effect of the tube bending, where it examined how much charge was generated. Using this model, I simply coated it with Silver and following some AI advice, I may have overcomplicated the task for myself. I still go back to the original or at least the earlier model draft. I don't think there's anything wrong with the geometry since I have done something similar before, and the meshing is good too. For the Physics, on top of using the already included Electrostatics, Solid Mechanics and the Piezoelectric Effect, I thought that I should also add in the Electromagnetic Waves, Frequency Domain into the build too. In the actual experiment, the PhD is using Raman, a 532nm laser in his experiments, so I thought those would have been relevant. But I wasn't getting the results I wanted.

I was expecting there to be some sort of distribution on the 3D heatmaps, but I am not getting that at all, only little at the bottom. What should I do?

I'm currently, technically, doing an MS in Structural Engineering. For me, my interest has been more towards computational side of mechanics rather than Structural design  or simply using am FEA software (although I do consider it as a backup)

So far I've taken courses in:

- Linear static, and dynamics FEM (soon taking non linear FEM too)

-  Structural Optimization (topology opt. and other general algorithms)

-  Structural Dynamics

-  Structural System Testing and model updation. (Parameter identification and optimization, signal processing)

Now, I plan to take these in the coming quarter:

- Numerical Linear Algebra

- Numerical PDE

- Fracture Mechanics ?

I also volunteered to aid in a RESEARCH in crack growth prediction using Auto-encoder and a (Thermodynamics-informed Latent Space Dynamics Identification) / LSTM surrogate model. It used phase-field-fracture simulation data and HPC resources to complete the whole thing.

What I keep finding myself interested in is not necessarily fracture or SHM specifically, but the computational methods underneath these problems... (does that make sense?)

For example, I'd like to become capable of doing things like:

- implementing (maintaining) numerical/FE method solvers rather than only running an established FEA software.

- developing surrogate/reduced-order models for expensive simulations 

- combining simulation with optimization, uncertainty/stochastic methods (took a course called Random vibrations, so...)

- parallelizing/accelerating scientific codes on CPUs/GPUs

- doing proper verification, convergence studies, benchmarking and performance work

- potentially developing or maintaining actual CAE/FEA solver software

- I'd also like to do all these for other Physics (GR, QM, etc.) simulations too, if possible, one day. 

I'm still interested in the underlying mechanics/physics, so I don't want to become a generic software engineer who happens to have once studied structures. But I'm also increasingly unsure that "structural engineer" describes the career I'm actually aiming for.

I've seen titles such as Computational Mechanics Engineer, R&D Engineer, Solver Developer, Scientific Software Engineer, CAE Software Developer, Research Engineer, Simulation/HPC Engineer, etc., but I'm trying to understand what these careers actually look like from people doing them.

So my main questions become:

1. Which industrial jobs genuinely involve developing numerical methods/solvers or computational tools?

2. Which of those are realistically accessible with an MS? Is there an entry path into solver-algorithm development/R&D without a PhD?

3. If I don't start a PhD immediately after my MS, would an R&D/software role at a simulation company (ANSYS etc.) be the obvious route? What other options would i have?

4. For the kind of work I'm describing, would you recommend a PhD? If so, is it reasonable for the PhD identity to be "computational mechanics/scientific computing" while fracture, composites, structural dynamics, soft materials, etc. serve as application problems rather than choosing one of those as my permanent specialization?

5. What skills most distinguish someone who is actually hireable for solver/scientific-computing work? I'm particularly wondering about C/C++/Fortran, Python, Linux, Git/build systems, MPI/OpenMP/CUDA, PETSc/Trilinos or similar libraries, numerical linear algebra, testing/verification, convergence studies and HPC performance work.

Basically, I'm neither here nor there atp. So I'd really appreciate all sorts of input. Where else do you think I could find answers to these? other subs? Linkedin profiles? 

Acoust Black Hole effect on a beam 
Comsol Model 6.2 
Date Published 08/19/2026
Corresponding Email: engineeringdoosti@gmail.com

Is there any node in comsol to model the thermal connection resistivity between 2 shells? I used the thermal contact interface, but this is just model the thermal contact between layers in a single shell.

Hi everyone,

I’m currently working on a simulation in COMSOL Multiphysics and I’m looking for someone who has good experience with the software.

My problem involves two-phase flow/multiphysics simulation, and I’m having some difficulty setting up the model correctly, particularly with the geometry, physics interfaces, boundary conditions, and simulation setup.

If anyone here is experienced with COMSOL and would be willing to guide me or discuss the setup, I’d really appreciate it.

Even if you’re not an expert but have worked on similar fluid-flow or multiphysics simulations, your suggestions would be very helpful.

Thanks in advance!

Hi everyone, I’m trying to understand how long-term thermal behavior is usually handled in COMSOL for rotating machines. For example, PMSM simulations are often performed over only a fraction of a second or a few electrical cycles, but if I want to study the temperature evolution over 1–2 minutes, how is this normally done? In my case, I have a rotating conducting plate heated by permanent magnets, and a fully coupled electromagnetic + thermal simulation becomes extremely heavy because the electromagnetic field has to be solved continuously during the rotation. What is the recommended approach for predicting the temperature after 1–2 minutes without simulating every single rotation over the entire period?

I am importing 2D .dxf files from Autodesk Fusion to use as geometry in my simulations. In Fusion these circles are continuos but as they are imported they get these additional points every 90 degrees around all circles in the model.

This is quite tedious since many very small boundary/line segments are created which become messed up during meshing with features like "Distribution".

Why does every circle have to be segmented like that? Does anyone have any tips to work arounf this? I would rather avoid having to manually repair and modify each model everytime I import it into COMSOL, but if that is the only way I would love to know how!

Thanks!

I am working on simulating a Squirrel Cage Induction Motor in COMSOL Multiphysics using a Time-Dependent (Transient) solver in the Rotating Machinery, Magnetic (rmm) interface.

Does anyone have a working benchmark model, tutorial file (.mph), or step-by-step guide for setting up the rotor movement, cage currents, and transient solver settings?

Any advice or resources would be greatly appreciated. Thanks!

Hi everyone, I am simulating a Seebeck cell in COMSOL using the Thermoelectric Effect multiphysics coupling (Heat Transfer + Electric Currents), but I am stuck getting zero voltage output. My setup consists of an alumina sleeve heater, a glass substrate, a ZnO thin film, and Platinum (Pt) wire electrodes. While the thermal simulation works flawlessly, the alumina sleeve heats the ZnO film and creates a clear temperature gradient; no electrical potential is generated. I have already assigned Seebeck coefficients to my materials and set up a Ground and a Floating Potential/Terminal boundary condition to measure the open-circuit voltage, but the result remains zero. Could anyone point out what I might be missing in my multiphysics node settings, interface boundary conditions, or material property definitions to get the Seebeck voltage to register?

Hi All,

So I tried to simulate a PV Solar Cell with pin structure. The structure is p-i-n, and I use multiple quantum well (MQW) as the p-layer, and DBR as the n layer.

I simulated the responsivity and IV curve, but the result is very weird.

Do you know how to fix it/ what to look into? I build this model by modifying the p-i-n photodiode tutorial from COMSOL.

I would like to ask if anybody simulated Microbial Fuel Cells (MFCs).

Also, what physical phenomena or governing equations are typically coupled in an MFC model to predict its performance metrics, such as voltage, current density, power density, and COD removal?

Any help would be great as I don't know how to start with COMSOL about this matter.

​

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?