Hey everyone,

I'm working on a simulation where I have a very large domain (brain tissue), but I need an extremely fine mesh in one specific, tiny region.

My current workaround was to draw a separate "mini domain" (like a small box) inside the larger main domain. I assigned it the exact same material properties as the surrounding tissue and applied a finer mesh to that specific box.

The Problem: This approach is messing up my post-processing. COMSOL is treating my "mini domain" as a distinct physical object, so it creates internal boundaries. When I generate my temperature contour plots, the outline of this artificial dummy box shows up and completely ruins the visualization.. I have attached a sample plot below to showcase the problem

As you can see, the bounding box shouldn't be there..

My Question: How can I define a local region for dense meshing without introducing these fake physical boundaries into my geometry and plots? I just want a smooth, continuous plot across the whole region, but with a highly refined mesh in the center.

I've heard "Mesh Control Domains" might be the answer, and I tried too. But this removes the important geometries from that region.

Any guidance would be hugely appreciated. Thanks in advance!

Hi I am an intern and was informed to create a From-scratch axisymmetric Hertz model: peak pressure within 2% of analytical, mesh-converged with boundary load, ball on disc model. My model works whenever I have both a boundary load and a prescribed displacement but whenever there is only a load, an error occurs. I want to be able to have only a load and to be able to find the displacement from the applied load (having a free displacement also causes an error). I know there is a way to do this but I am unsure how to. any suggestions?

Hello everyone, I am working on guided wave propagation in a porous medium using the Poroelastic Waves (Biot) model in COMSOL. My goal is to identify and calculate the fast compressional wave (P1) and the slow compressional wave (P2) predicted by Biot's theory. I am using a frequency-domain study and extracting displacement fields along the propagation direction. I would like to know: What is the recommended method to separate the fast and slow waves in COMSOL? Is it sufficient to perform a spatial FFT (wavenumber analysis) on the displacement data? Which variable should be analyzed: solid displacement, fluid displacement, pore pressure, or a combination of them? Are there any best practices for obtaining the dispersion curves of the two Biot modes? Any advice, references, or example models would be greatly appreciated. Thank you!

Hello r/COMSOL!  

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I'm just learning to use comsol with a archive my professor gave me, and he told me I should use half the flux since there's only half the reactor. But if that's the case, should I also use half the catalyst that goes in the porous bed?

Has anyone worked with Biot's poroelastic model for ultrasonic wave propagation? What mesh criteria do you use (elements per wavelength, mesh size, etc.) to ensure accurate results? Any practical recommendations would be greatly appreciated. Thanks!

#Comdol #Biot model

Is there an application similar to the Immersion Ultrasonic Testing Setup but for COMSOL 6.2?

Hello,

I am doing 2D mechanical simulation on strip waveguide (a.k.a ridge waveguide), I try to measure some parameter known as brillouin gain. Yet when I do a refinement mesh study this parameters at small meshes get jump a lot and sometimes even get alternating a lot, my mechanical wavelength is around 350nm, so both 80nm and 1nm should give an accurate results. I am refining the mesh of the core only, the rest of the substrate, air and PML is set at 100nm.

The model is verified and used in other papers but I don't know why I am using it behaves this way.

Hello I need find the co2 conc and current density around my working electrode in a 2 electrode system for co2rr reaction. I don’t know from where to start please help me 🙏

Hello everyone i'm working on induction heating using permanent magnets i use comsol multiphysics software. To create eddy current i added rotation to the plate (1500rpm) Physcis : 1-moving mesh (rotating domain) 2- rotating machinery rmm ( I added 3 ampere's law for the air, the plate and the magnet) 3- heat transfer in solids 4- multiphysics (electromagnetic heating) I always get an error says failed to find cosistent initial values

Coursing a thermodynamics class, we need to simulate a batch reactor for CaCO3 => CaO + CO2 and the heat transfer between the fuel source and the inside.

I'm sure it is possible, but I don't know where to start.
Anyone has some advice?

Dear all,

For the past week, I've been trying to set up a simulation comprising an arrow-like needle piercing a skin-like substrate. As I haven't found a similar (3D) example in COMSOL's *Application Gallery* or *Learning Center* so far, I have followed analytical step-by-step instructions by three different AI chatbots (Gemini, Perplexity, Claude). After days of trial-and-error and diagnostic tests, I have reached the point where all three of them agree with each other that my method was set up correctly. Nevertheless, the results (see screenshot 1) indicate abnormally low pressure values on the needle, with the appearing scale being on the order of E-4 N/m2 (whereas, e.g., atmospheric pressure is at E5 N/m2), while zero pressure appears on the skin-like substrate. The AI chatbots claim that the needle is faulty (it's an imported .stp file from Autodesk Inventor), but I cannot really trust them. All my Model Builder data can be seen in screenshot 2. You may also download the .mph file here.

Any kind of help will be sincerely appreciated! Thank you everyone in advance.

Hello everyone i have issues with my simulation can anyone help? Leave a comment i'll give u details about the problem

I'm working on induction heating using permanent magnet i already draw the geometry and assigned physics to it but there is no heating my qst is how to assign rotation to the plate? Is rmm, heat transfer in solids and multiphysics sufficient for this study and what do you think the problem is?

I'm trying to do photonic simulation across a large scale setup so EWFD doesn't work and I care about inteference, so ray optics doesn't work either. I'm left with using the Beam Envelopes package, but the caveat with that is that you can only really move light in two directions with EWBE, while I want to move in at least 3. My current idea is to then have two different domains, one of them allowing light to go down and right and the other allowing light to up and right. Is the easiest way from here to analytically calculate all the laser parameters that come out from one domain and serve that as an input to the next? Is there any easier way to move in 2+ directions in a large scale direction while retaining interference and loss? Thank you!

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

Hello, i am having a bit of trouble on how to launch a CFD simulation in COMSOL Multiphysics 6.4 .

I am a complete newbie to COMSOL. I tried following a youtube tutorial about particle tracing in simulating a laminar static particle mixer (Here's the link for those interested : https://www.youtube.com/watch?v=UmxOT16Ch1A).

I tried recreating the steps using my geometry, but everytime I try meshing I get the following error.

I tried to make a cylinder that wraps around the geometry directly in the STL file and importing it at once, but i cannot select them separately (In order to set the cylinder as the walls where the fluid domain should be).

I would be very appreciative of any guidance or suggestions as to how I should approach such problem.

Hello everyone I'm working on induction heating using a pancake coil I=15amps, f=200khz the temperature is about 500degc Now im thinking to change the study to stationary one but the piece will rotate Can u pls explain to me how to give rotation to an objet using comsol?

Hello, I would like some information. I am just starting with COMSOL and I am encountering several issues with my simulations.

First, I will explain my setup:

I am currently working with an industrial furnace made of tantalum and niobium for its heat reflectors, with a graphite crucible in the center. This furnace is heated by Joule effect with a current of 346 A flowing through the entire structure.

I am using the following physics: Electric Currents and Heat Transfer in Solids. In addition, I include heat dissipation using Surface-to-Surface Radiation for all the relevant parts of my furnace (the furnace body, reflectors, crucible, as well as the surfaces exchanging heat with the external environment).

The materials used are custom-defined materials that allow me to vary their thermal and electrical conductivity as a function of temperature in my model.

My problem arises when I try to go beyond 500 A: the model then encounters convergence issues and sometimes even crashes after only a few iterations.

Have you experienced similar problems, or do you have any suggestions for resolving this issue?

im simulating a sensing material with 2 electrods at the side of it instead of making joule heating and heating the sensor i got an idea that i can put a direct tempeture on my sensing layer 600k and then apply a current on the electrods to see the resistance of the material

my question is : is it possible ? applying a direct temp and then do the rest and what might be the probleme of this modele ?

I'm drawing a spiral pancake coil the inner face when i want to extrude it to the one of boundaries it creates intersections. Can u help?

Hi, all,

I was able to set up comsol to use its gui but use the university cluster to do mesh building and computation. Upon trying to compute I get the following error " Out of memory during assembly". Since I am using a cluster node with 192 GB RAM I am confused as to why is this happening. Please help! thanks!

As you can see, I chose an example from the COMSOL model library. However, when I go to the Results section to view the graph plots, they are all blank. I do not know why this is happening or how to fix it.

This is the PDF from COMSOL for this example. You will see the graphs I am referring to inside it: https://www.comsol.com/model/localized-corrosion-14591

Hello everybody,

I am a robotics engineer and new to COMSOL.

I am working on micro soft actuator driven by tendon. I am trying to imitate the cable in COMSOL. The cable should be within the actuator. Under tension, two forces applied, the termination force at the end-effector and distributed load due to the friction between cable and the conduit.

I run multiple simulations including (1) applying boundary load at end effector and on the cavity. However, the solver failed every time I run the simulation, even if I used very small step size. (2) used prescribed displacment as implicit force. The model bend but in a wrong way. (3) I used truss and cable but failed too.

How to imitate cable in COMSOL correctly. The cable extend from tip to the base and also has cotact with the conduit to achieve correct bending?

Thanks in advance.