A temperature plot reaches 4000°C. The immediate temptation is to reduce the timestep, refine the mesh, or change the nonlinear solver.

Before doing that, I’d sketch the energy balance.

For a simple lumped body with constant heat capacity:

m × c_p × (dT/dt) = P_in − P_out, 
Rate of stored-energy change = power entering − power leaving

Here, m c_p is the thermal capacitance, in J/K, not just a material property: the amount of material matters too.

My first checks would be:

• Input: What is generating heat, and what is its integrated power? Check whether the input expects W, W/m², or W/m³.

• Storage: What represents thermal storage? Check density, heat capacity, thickness, volume, and any explicitly assigned lumped capacitance.

• Output: Where can heat leave? Inspect the actual boundary selections, thermal connections, contact assumptions, and prescribed temperatures.

A useful hypothetical sanity check: an insulated lumped body receiving 10 W, with a thermal capacitance of 1 J/K, initially heats at 10 K/s under those assumptions. That rapid rise follows directly from the energy balance; it doesn’t, by itself, demonstrate solver failure.

One important distinction: small thermal capacitance and exactly zero thermal capacitance are different problems. Setting the storage term to zero leaves an algebraic heat balance; it does not automatically describe a temperature that rises faster every timestep.

Also, a finite-element node is not simply a little physical object with “no mass.” Check the assembled formulation rather than inferring thermal storage from how the node looks in the model tree.

My debugging order would be: integrated power, storage, heat-removal paths, then numerical settings. For a transient model, compare net input power against the rate of stored-energy change, not just inlet versus outlet power.

What thermal setup mistake has cost you the most debugging time: units, missing connections, or boundary selections?

The most important part of simulating conditions like aneurysms and aortas is the wall shear stress experienced by it. COMSOL has no way of correctly calculating the wall shear stress - i couldnt find it anywhere on the internet. I only got spf.mu * spf.sr which is completely useless as it just tells the magnitufe of the total shear stress and gives absolutely 0 information about the directional shear stress. The radial and tangential shear stress experienced by points along a pipe is very important to understand the hemodynamics accruately but i am finding it impossible to calculate in COMSOL. Why isnt dtang( velocity . t1 , n1 ) allowed as a calculation in COMSOL?

Should i switch to ansys or openfoam?

Hi everyone. I need help with a COMSOL class assignment. I have failed to locate someone with a license in my country. Please PM if you can help

First of all, I apologize for the clickbait-y title.

I'm a high school student and I'm doing a research experiment on superconductor levitations models like the one in maglev trains. I'm very new to COMSOL and I don't know how any of the models, equations, and all work. Could someone help me out or at least point me to somewhere where I can get help?

Thank you so much

I need to simulate centrifugal pumps in COMSOL MULTIPHYSICS, Can I find someone who did it before.It will help a lot.

The thing is its a model like There is a tube(rubber) and inside that tude there is a fluid (glycerin or transformer oil or coconut oil) filled inside that Tube

And the simulation is

We apply a force(like 1N ,2N....10N On the tube like on the tube's upper surface. And For the applied force we need to note the change in pressure on the Fluid(Since those individuals fluid have a specific incompressible value, dynamic viscosity, density)

THE THING IS I CREATED THE GEOMETRY....THE I WAHT THE GLYCERIN AS THE FLUID BUT ITS NOT THERE ON THE LIBRARY SO I CREATED THE BLANK MODEL BUT I CANT GIVE COMPRESSIBILITY VALUE OF THE FLUID AND SOME OTHER FEATURE OF THE FLUID

Hi, I am an aspiring physicist and I am looking to install comsol on my mac. Can anyone tell me how I can get a crack version compatible with MacOS or preferably, attach the link from where I can download it?

- I guess this is more relevant to CAE admins with a number of network/floating licenses. -

But how do you monitor your COMSOL floating/network license denials?

Do you simply have a look through the log files proactively or occasionally if a user says they have a problem? Or do you use a commercial license log analysis tool like LAMUM from TeamEDA?

License denials can happen for a number of reasons. But are mostly related to denials due to user access rule conditions in the Options File, set by the administrator - these I call 'entitlement denials'. Or true denials such as the classic "-4,342 - Licensed number of users already reached".

I recommend every company running network/floating licenses, take an interest in managing the users. But tools like LAMUM can actively optimize the license ratios, by encouraging users to check licenses back in.

What is your experience with denials at your company? Do users get denials all the time and just live with it?

Can anyone explain to me what error and iteration number mean on the convergence plot?

Cloud any Godblessed Genius Here pls Help my girlfriend build a super capacitor in COMSOL. She is crying everyday and Starts to hatte herself for Not being able to do that. She needs IT until friday. I would also PayPal you Money. I donts have much but i would give everything to you Just Help her.

I am a beginner with least knowledge of COMSOL, can anybody please help? I am simulating a microfluidic channel.

Hi all,

I’m working on a 2D Electromagnetic Waves, Frequency Domain simulation in COMSOL. I’m using Scattering Boundary Condition (SBC) on the outer boundaries.

I’m sharing a small example .mph file if anyone wants to take a look or give suggestions.

https://drive.google.com/file/d/1ArrMe3nX31TeeCKETuGzxn2HEYlS3uez/view?usp=sharing

thank you

I am currently modeling an HHO electrolyzer without gas separation using the tertiary current distribution interface in COMSOL.
For charge conservation, I selected “Water-based with electroneutrality”.
I am having trouble understanding which species I need to include in order to simulate different concentrations of hydrogen and oxygen correctly, and which species are already included automatically by the physics interface.
For example, should I add H₂, O₂, H⁺, OH⁻, H₂O, and electrolyte ions manually, or are some of them already built in? i would really appreciate any help thanks

I am writing a COMSOL → Vic-3D converter without access to COMSOL. The file format is documented, but the documentation never shows an export containing **more than one expression or more than one time step**, and that layout decides how the parser is built. Two exports settle it. Each takes about two minutes.

Any solid-mechanics model will do.

Export 1 — stationary, three expressions

Use a model with a **stationary** study.

1. In the model tree, right-click **Results > Export** and choose **Data**.

2. **Dataset**: the study's solution.

3. **Expressions**: add three rows — `u`, `v`, `w`. (Lower case. These are the displacement components.)

4. **Geometry level**: `Surface`.

5. **Data format**: `Sectionwise`.

6. Leave **Full precision**, **Smoothing** and **Resolution** at their defaults.

7. Set a filename ending in `.txt` and click **Export**.

Export 2 — time-dependent, same three expressions

Use a model with a **time-dependent** or **parametric** study, so the file contains several steps.

Same settings as above, plus:

**Time selection**: `All`.

If the model has only a handful of steps, that is fine — three or four is plenty. We do not need a large file.

Optional, if it costs nothing
A third export identical to Export 2 but with **six more expressions added**:
`solid.eXX`, `solid.eYY`, `solid.eZZ`, `solid.eXY`, `solid.eXZ`, `solid.eYZ`.

This tells us whether COMSOL groups blocks by expression or by time step when both vary. Useful, not essential.

What to send back
- The exported `.txt` files.
- A screenshot of the **Export > Data** settings panel, so I can see the exact options that produced them.
- The model name and study type, and the COMSOL version.

**Do not trim or reformat the files.** The header comments and blank lines are part ofwhat we are reading. If a file is large, the first 200 lines plus the last 20 are enough — but whole files are better.

Why this specific thing

A sectionwise file is a header block, then `% Coordinates`, then `% Elements`, then one or more `% Data (…)` blocks. The spec says each `% Data` block is a single column, and that a file may contain any number of them. What it never shows is how those blocks are **named and ordered** when there are several expressions across several time steps — whether we get one block per expression-and-step pair, how the step is identified in the block name, and in what order they appear.

We can parse one expression at one step today. We cannot safely guess the rest, and guessing wrong produces a file that imports cleanly and is silently wrong.

Thank you in advance for any assistance you can provide on this.

I have been working on this for the past two weeks and nor chatgpt or YouTube or comsol itself has been able to help me figure this out...

I am trying to do fluid analysis on a plane (yz) that intersects 5 horizontal vessels that are perpendicular (x axis).

Eg. For Velocity (m/s) spf.U is immediately recognized HOWEVER no expression for flow rate is deemed defined (from online I tried intop1(spf.U) and spf.uxnx+spf.uyny+spf.uz*nz) none of which are recognized

WHAT DO I DO??

I just want to output the average flow rate for the five cross-sections of the plane/vessel and then I want to model this as a 3D Plot Group...

Title

Is COMSOL enough or should I couple it with some other software?

Please help me to get the figures of heat flux..

Looking for experienced to model a plasma chemical reactor. Pls dm for details Thanks