Latest Discussions - COMSOL Forums

Adding Sheet Resistance

Tue, 04 Nov 2025 14:45:42 +0000

Hi, I want to add sheet resistance to my simulation. The thickness of substrate 1mm and above which there is printed ink structure having a sheet resistance value say R_s. I want to obtain the microwave reflection characteristics of the FSS. There is no option to add sheet resistance. (In impedance boundary condition or in transition boundary condition there is only option to add conductivity (S/m)) not sheet conductivity(S).) The thickness of the ink layer is unknown to me and it is very small compared to the thickness of substrate. Is there any way to add sheet resistance. (may be through some boundary condition or structure or any other way)

Use solution of one study as initial particle position for another without exporting

Tue, 04 Nov 2025 10:06:49 +0000

Hello there,

I am currently working with the Mathematical Particle Tracing module, although this question extends to at least the Charged Particle Tracing module.

Is it possible to use the final particle positions from one study as initial positions in another study without using the "Release from Data File" function?

I have an assembly split in two because one features rotating parts and uses the Rotating Frame domain while the other half does not. I will have to run this simulation for different values, maybe with a parametric sweep, so having the workflow a bit more streamlined would be a great time saver.

Thank you all in advance.

Request for Trial Access — Electrochemistry / Electrolyzer Module

Mon, 03 Nov 2025 17:49:53 +0000

Hi COMSOL Team,

I am a PhD scholar (Chemical Engineering) at IIT Kharagpur. Our group currently uses a COMSOL license but we do not have the Electrochemistry / Electrolyzer Module. We are evaluating purchase of this module and would like temporary trial access to test our models and confirm fit before buying.

Could you please provide details on trial availability and the process to enable the Electrochemistry / Electrolyzer Module for our license?

Thank you, Rajeev Ranjan PhD Scholar, Dept. of Chemical Engineering IIT Kharagpur

excessive virtual memory on macOS on Apple Silicon Macs

Mon, 03 Nov 2025 12:42:10 +0000

I'm running Comsol Multiphysics on macOS, tested on two Apple Silicon Macs: an M1 Air with 8 GB RAM and an M3 Air with 16 GB RAM. In both cases, Comsol reports around 450 GB of virtual memory available, while the actual physical RAM is correctly recognized.

So far, I haven’t encountered any simulation errors or crashes - everything runs normally. It seems the reported value represents the addressable virtual memory rather than real physical memory, which might be misleading but does not appear to affect performance.

Is it possible to introduce an abrupt potential change at an interior boundary?

Mon, 03 Nov 2025 07:41:22 +0000

Hi all, when I handle an electrostatic double layer, i.e., a thin dipole layer, the potential would abruptly change across the interior boundary, is it possible to handle such a discontinuity for the classical PDEs or the electrostatics module? Thanks.

seismic aquifer response

Mon, 03 Nov 2025 07:25:19 +0000

Hello, I want to simulate the subsurface temperature changes caused by earthquakes. I suppose the approach is to first simulate the equilibrium state of the study area under natural conditions in Study 1, then add the influence of earthquakes in Study 2 to observe the evolution of subsurface temperature. However, I have encountered some troubles with the simple initial state. Should the initial flow field be relatively stationary on a large scale? But there is always an initial flow field in my simulation.How to build a sample well-aquifer model with a stable state?

Integral of a distance field over domain as boundary condition

Fri, 31 Oct 2025 06:58:45 +0000

I'm dealing with a Laplace problem on a domain with a Dirichlet boundary condition. And the boundary value is given by , where is the distance between the points and ( may be a subset of ). Any hints on the solution? Thanks.

Photonics Research

Thu, 30 Oct 2025 15:05:35 +0000

Hi, I am a Ph.D. student. How to learn COMSOL Multiphysics for photonics research?

Lift and drag on a plate

Thu, 30 Oct 2025 06:04:35 +0000

I am working on a problem with rotating aluminium plate beow a stationary halbach magnet array inside a cylindrical air domain. I am tryinf to calculate the lift and drag experienced by the plate, but i am getting the following error?

Undefined variable. - Variable: comp1.rmm.tAY - Geometry: geom1 - Boundaries: 8, 10-11, 181 Failed to evaluate Jacobian of expression. - Expression: comp1.rmm.tAY Failed to evaluate Jacobian of operator. - Operator: comp1.src2dst_ap3 - Geometry: geom1 - Boundaries: 312-317 Failed to evaluate Jacobian of expression. - Expression: ((comp1.spatial.invF11(comp1.rmm.tAX-comp1.src2dst_ap3(comp1.rmm.tAX)))+(comp1.spatial.invF12(comp1.rmm.tAY-comp1.src2dst_ap3(comp1.rmm.tAY))))+(comp1.spatial.invF13(comp1.rmm.tAZ-comp1.src2dst_ap3(comp1.rmm.tAZ))) Failed to evaluate Jacobian of expression. - Expression: if(comp1.incontact_ap3,comp1.spatial.invF11(comp1.rmm.tAX-comp1.src2dst_ap3(comp1.rmm.tAX))+comp1.spatial.invF12(comp1.rmm.tAY-comp1.src2dst_ap3(comp1.rmm.tAY))+comp1.spatial.invF13(comp1.rmm.tAZ-comp1.src2dst_ap3(comp1.rmm.tAZ)),0)

Undefined variable for Heat Transfer in Solids error

Wed, 29 Oct 2025 13:39:03 +0000

Hello, I am getting this error even when all the variables are defined. COMSOL should automaticaly create qy and qx. This is the error:

Undefined variable. - Variable: ht.qy - Geometry: geom1 - Boundaries: 17, 24, 41, 60, 73, 91 Failed to evaluate expression. - Expression: ht.qy Failed to evaluate expression. - Expression: comp1.intopY(ht.qy) Failed to evaluate expression. - Expression: comp1.intopY(ht.qy) - Feature: Global Evaluation 1

linearized resistivity alongside homogenized coils

Mon, 27 Oct 2025 16:43:50 +0000

I'm trying to model an underground cable and I want to use the homogenized multiturn coil model to calculate for a milliken conductor but I also want the copper to account for the rise in temperature. Unfortunately the homogenized model does not allow for a linearized resistivity calculation which I believe to be because it requires the resistivity to be constant across the surface. This seems to leave 3 options - average the temperature across the surface, manually create a linearized resistivity function within the coil settings or create each strand of the cable individually and treat each as its own coil. Anything I'm missing or any suggestions welcome.

Suggested improvement: sound signal

Mon, 27 Oct 2025 09:11:20 +0000

I work with a lot of large models where the time to import via LiveLink, meshing, making Form Union and not least solving take extensive time.

Since I am not about to stare idly at the program for a quarter of an hour waiting for LiveLink to process, I switch over to other duties. On the same PC - meaning that the COMSOL window is minimized or in the background - or on my communications laptop.

Doing so, I have little to inform me that the currently processed operation has ended but the sound of the CPU fan, and it is not that prominent nor reliable as an indicator.

So it would be great if one could toggle an option in the settings where some chime would sound when operations are finished. Small "ping" for every node in the Model Builder, or a more pronounced one for longer operations such as solving, meshing, Form Union or whatever. Best of all if it could be customized.

Friendly, /M

'Not Responding' encountered when canceling the calculation in the 'Progress' window

Sat, 25 Oct 2025 13:58:21 +0000

Hi there,

I am performing time-dependent modeling using MATLAB script with LiveLink for MATLAB, during which a command "ModelUtil.showProgress(true)" is run to call the Progress window for the convenience of monitoring the progress.

After several days' calculation, I pressed the Cancel button and tried to evaluate the situation, but something seemed to be stuck and the 'Progress' window becomes in the state of 'not responding' while neither COMSOL server nor MATLAB is running (see the attached screen snapshot).

The question is:

1) Is it possible to salvage this situation? I have encountered this situation before. If the 'Progress' window is forced shut down, the COMSOL server will go with it and I won't be able to know the calculation results of several days' running.

2) Is it possible to avoid such situation? I have recently encountered this situation quite frequently.

Any suggestion would be most welcome.

Best

Wall Deposition

Thu, 23 Oct 2025 15:22:05 +0000

Hello,

I’m currently trying to visualize aerosol deposition in the laminar flow regime using Particle Tracing for Fluid Flow in COMSOL, aiming to validate experimental results from a nebulizer-based setup.

My model consists of a cylindrical pipe (radius = 1 mm, length = 6.7 mm) with air flow velocity = 0.03 m/s. I’m simulating 0.5 µm particles with Stokes drag and Brownian motion enabled. However, I’m unable to observe significant deposition under these conditions. Interestingly, deposition increases sharply when gravity is included.

Has anyone successfully modeled nebulizer-like aerosol deposition in a laminar airflow field? Are there recommended settings or modeling approaches to better capture near-wall deposition without relying solely on gravity?

I’m also considering switching to the Transport of Diluted Species interface for a continuum approach to diffusion and deposition, and I’d appreciate any insights or comparisons from others who have tried this.

Ultimately, my goal is to compare cylindrical vs. rectangular channels to understand how geometry affects deposition patterns.

Thank you in advance for your suggestions and experiences!

Concrete plastic deformations without Geomechanics Module

Thu, 23 Oct 2025 09:56:34 +0000

Hello, I’m new to COMSOL and currently trying to perform a flexural analysis of a concrete beam. I would like to ask whether it is possible to accurately model the plastic (nonlinear) behavior of concrete without having access to the Geomechanics Module. From what I have read, the Smeared Crack Model and Damaged Concrete Model are available only through the Geomechanics Module, while the default material models such as von Mises or Tresca seem to be more suitable for metals, not brittle materials like concrete. Is it possible to simulate plastic deformations or cracking in concrete using only the Structural Mechanics Module, or is the Geomechanics Module required?

Thank you for your help

Minor Dataset issue

Wed, 22 Oct 2025 20:23:54 +0000

I have a minor dataset issue:

I am running the same model in COMSOL 6.2 on 2 machines running the same OS. On one machine, when I compute a new study it makes a new dataset in the results. With the other, the study overwrites the previous dataset with the new results. Where is the preference that controls this behavior? I prefer a new dataset with each study.

Geometric Optics Imaging through medium

Wed, 22 Oct 2025 16:22:29 +0000

Very new to COMSOL geometric optics, trying to model how an image looks after a cross grating / scattering medium / absorption layer domain or boundary. At first I want to keep it as simple as possible and looking for insight to support my challenges. All of my Multiphysics experience thus far has been in wave optics module.

To keep it as simple as possible for now the optical train would be image plane -> medium -> lens -> ray detector. I was able to compute ray trajectories previously, but some troubleshooting change i made to the physics broke things and now am getting an error each run time that prevents ray trajectories from being plotted. Advice / insight / applicable models to point to and learn from are all helpful. I already tried adapting the double gaussian lens for my purpose by adding an additional film domain right in front of the image plane but that seemed to have broken things.

Objective: Input scattering medium or cross grating parameters to model image formation through the medium. Idealistically similar to the double gauss lens tutorial results where the image and formation are next to each other.

Branch Flow Statistics in Fluid Simulation

Wed, 22 Oct 2025 08:47:54 +0000

In fluid simulation, the model has one inlet and one outlet, with 90 branch pipes in the middle. How can I quickly calculate the flow rate of each branch pipe in the middle? Thank you for your help.

S parameter extraction from 3D model + external circuits

Mon, 20 Oct 2025 19:00:11 +0000

Hi everyone,

I’m modeling a two-port piezoelectric resonator that functions as a transformer (per the mBVD representation). I’ve connected the device to an external matching network with a series inductor at the output to cancel Cout, and I’d like to extract the S-parameters of the combined device.

So far: Using Terminal (power) with Terminated boundaries on the 3D structure gives me S-parameters for the bare 3D model only, not the coupled device-and-circuit.

I also tried an Electromagnetic Waves, Frequency Domain (EMW) study, but I’m not confident this is appropriate for a primarily lumped, electromechanical two-port with an external circuit.

Question: What is the recommended workflow to obtain S-parameters when a 3D piezoelectric resonator is connected to external circuitry?

Thank you for any guidance.

induction heating

Sun, 19 Oct 2025 06:52:30 +0000

Why, during the process of conducting the simulation of workpiece induction heating, as the workpiece moves, the temperature of the induction heating part of the coil keeps rising continuously, and it fails to reach a state where the heat input and output are balanced, thus preventing the temperature at the heating location from remaining constant.The 2-D rotational modeling that I use.Set up heat radiation and heat flux for heat dissipation. Thanks for help!