Latest Discussions - COMSOL Forums

Problem with Adaptive Mesh Refinement in Phase Field Simulation

Mon, 03 Mar 2025 06:16:54 +0000

Hi,

I have been trying to simulation a phase field equation coupled with temperature which are essentially two heat equation (parabolic) form with coupling in the form of having their respective variables in the other physics. I have used Weak Form for both the equations on COMSOL 6.2 and tried automatic mesh refinement to make the mesh finer around the interface as the interface grows in a time dependent study.

Unfortunately, there seems to be not much of detailed blogs here explaining the mesh refinement module and where to apply its respective options. I am not sure how i am getting the result I am or how to troubleshoot it. I have attached the mph filed for reference and also the equations I am using to simulate. Any help is highly appreciated.

Thank you so much!

Antenna calculation

Mon, 03 Mar 2025 05:03:50 +0000

Hello, I would like to ask for some advice. I am currently using the Electromagnetic Waves, Frequency Domain (RF Module) to build an antenna, with the frequency range set to 0.7 GHz - 5.1 GHz and a step size of 0.6. The calculation is very slow, but it eventually results in an error. The error message is: "Feature: Stationary Solver 1, failed to find a solution. The linear iteration diverged. The returned solution does not converge. Not all parameter steps were returned." Could you please tell me what might be causing this? Is it an issue with the model? Thank you very much!

dew point evaporative coller

Mon, 03 Mar 2025 05:01:45 +0000

I am trying to simulate dew point evaporative cooler which is having dry and wet air channel separated by thin material wet air channel which is coated with porous material what are the physics involved in this and how they couple please guide me

MEMS Bistable Switch

Mon, 03 Mar 2025 04:25:53 +0000

Hi guys,

I am trying to build a MEMS bistable switch using curved beam. In stationary study, the graph of reaction force vs. displacement has shown a bistable behaviour. In time-dependent study, I apply the prescribed displacement to a block which is meant to push the bistable structure but keeps getting error message like "Nonlinear solver did not converge. Maximum number of Newton iterations reached. There was an error message from the linear solver."

Is it possible to see the bistable structure snap-through process in comsol since I never see an example? If so, what should I do to fix the problem.

Thank you.

Antenna calculation

Sun, 02 Mar 2025 09:11:35 +0000

Hello, I would like to ask for some advice. I am currently using the Electromagnetic Waves, Frequency Domain (RF Module) to build an antenna, with frequency ranges set to 0.7 GHz - 4.9 GHz and 0.7 GHz - 5.1 GHz, and a step size of 0.5 for both. In these two frequency ranges, the calculated results for the S11 parameter and voltage standing wave ratio (VSWR) can only be computed up to 4.7 GHz. Additionally, the resonant points calculated in both frequency ranges are the same, and the values corresponding to each resonant point are also identical. Could you please tell me what might be causing this? Is it only possible to compute up to 4.7 GHz, or is it an issue with my designed model? Thank you very much!

Chemistry (Chem)

Sat, 01 Mar 2025 23:57:43 +0000

The below post is related to an archived discussion

Hello,

i cant seem to find the Chemistry (Chem) on my comsol software. please help.

OSI in COMSOL

Sat, 01 Mar 2025 15:21:00 +0000

Hello,

I am simulating intracranial artery. I need help to calculate OSI in COMSOL. I calculated WSS with tis expression: WSS = sqrt(spf.K_stressx^2 + spf.K_stressy^2 + spf.K_stressz^2). It worked for me. Is it right?

For OSI I tried this: OSI = 0.5 * (1 - abs(timeint(0, T, WSS)) / timeint(0, T, abs(WSS))), it is not working, unless I am doing it wrong. Can someone help me to calculate OSI step by step? I would be very thankful.

Marangoni Effect

Sat, 01 Mar 2025 13:27:27 +0000

Hi, I am modeling an evaporation simulation where the Marangoni effect should be accounted for. I have one complete model that runs perfectly for the constant surface tension value, but as long as I make the Surface tension temperature-dependent, my film starts to tear, and it won't converse.

Does anyone have any idea what it should change?

Best Regards, Ishwor

Flow between parallel porous slabs and transport - Select Physics

Fri, 28 Feb 2025 05:00:16 +0000

Hello,

I am trying to simulate the flow of a gas mixture in such a way that - the gas mixture flows in a channel, - then is in contact with the slabs of porous medium, - then flow between parallel slabs of porous medium, - finally exiting into a channel without any porous medium.

I have attached a figure to illustrate this.

I would like some help clarifying if I should set up the physics as a combination of "Transport of Dilute Species in Porous Media (tds)" and "Free and Porous Media Flow, Brinkman (fp)"? Or, "Transport of Dilute Species (tds)" and "Free and Porous Media Flow, Brinkman (fp)"?

Thank you.

Modeling Particle tracing in fiber filtration

Fri, 28 Feb 2025 02:59:38 +0000

Good morning dear all,

I am simulating Particles Tracing by COMSOL Multiphysics and I want to see the field of attraction of particles around a fiber and evaluate the particles transmission probability by fiber filtration.

I will be grateful if someone can help me.

Best regards !

Instability when modelling gold in the wave optics transient model

Thu, 27 Feb 2025 14:19:28 +0000

Dear COMSOL Forum

I am trying to simulate a gaussian pulse incident on a gold surface using the wave optics transient model. I created a model based on this tutorial: https://www.comsol.com/model/second-harmonic-generation-of-a-gaussian-beam-wave-optics-14701 and then added a material in the second half of the domain. As the wave optics transient model only uses the real part of the permittivity, I am inputting the imaginary part via a conductivity value instead. When I put in permittivity/conductivity values for a semiconductor the simulation runs well, showing a reflected and transmitted beam with the transmitted being slowly absorbed with distance. However, when I put in permittivity/conductivity values for gold the simulation initially runs, but then the electric field in the gold region becomes unstable - in some small region (and before the beam reaches the surface) the electric field strength rapidly goes to infinity and the simulation crashes. I have tried reducing the mesh size and timestep significantly, but this seems not to resolve the problem. Would someone be able to suggest a method to solve this?

Many thanks in advance.

Best wishes,

Alan

Integrating semiconductor and magnetic fields module

Thu, 27 Feb 2025 13:23:11 +0000

I want to analyze the impact of magnetic field on a Si block (1x1x1 um) with doping density variation subject. The questions are as follows: 1. What would be the simplest way to integrate the semiconductor module with the magnetic fields module to achieve the above? 2. Is there a way to specify the doping distribution without using the semiconductor module, eg just in the material definition of Si, so as to avoid the semiconductor module entirely? Would this make the analysis less precise?

[Solved] Dependent Variable Field in The Pressure Acoustics, Time Explicit (pate) also discontinuous Galerkin method?

Thu, 27 Feb 2025 12:52:39 +0000

Hello!

When using a 'Dependent Variable Field' directly in the 'The Pressure Acoustics, Time Explicit (pate)'* physics interface, will this new extra dependent variable (from 'Dependent Variable Field') also be calculated with the discontinuous Galerkin method (dG-FEM)?? When for example using 'Dependent Variable Field' for a domain.

*which uses discontinuous Galerkin method (dG-FEM) for the standard dependent variables

Nice greetings

piezoelectric ceramic ring

Thu, 27 Feb 2025 03:21:06 +0000

I want to make a piezoelectric ceramic ring, first of all, it is free to vibrate in the air. The simulation will affect the thickness vibration as well as the radial vibration after I add the top and bottom caps to it, but what I want to achieve is that the top and bottom caps will only affect the radial vibration of the middle piezoelectric ceramic ring and not the thickness vibration, how should I set this up, the physical fields that I am using are Pressure Acoustics-Frequency Domain, Solid Mechanics, and Static Electricity.

Laminar flow. 4 inlets for 1 vessel

Wed, 26 Feb 2025 16:30:25 +0000

Hello,

A vessel has 4 inlets. Flow rate in parameter table is F and 4 inlets were selected. Question: the F is for each inlet or F/4 only?

Thanks,

Vladimir

COMSOL export rounds frequency data in datapoint headers

Wed, 26 Feb 2025 13:57:43 +0000

I did a study using frequency domain for different frequencies. Screenshot of setup:

When I plot the data inside, it looks fine.

I exported the data as a .csv file with the "Full precision" setting on. However, this seems to only impact the values defined in the "expressions" section and not the frequency data.

The exported table contains datapoints inside the .csv table that are formatted like this:

intop1(ec.Jz/E0/a^2) (S/m) @ freq=1.2589E5, s=0.01 0.05118908008352398+5.732703179902605E-4i

I used the "@ freq=1.2589E5" part of the datapoint header to read the frequencies. I plotted the data in python with the exact same operations performed on it, which resulted in the following graph, which looks bumpy:

The reason for this is that the 5 decimal places of the frequency in the datapoint header were too imprecise for my use-case. The solution was to export not only the simulation results in the "expressions" tab, but also the frequency by just adding "freq" as an expression, which will export it with full accuracy. This is probably completely obvious to 99% of you, but I was so confused why my graph looked bumpy with the exported data.

How to set up the phase transformation field for laser cladding with two different materials?

Wed, 26 Feb 2025 13:30:31 +0000

When simulating laser cladding using COMSOL, if the substrate and the cladding layer are made of two different materials and phase changes need to be considered, how should the expressions related to the phase transformation field be set for both materials in the simulation of the temperature field and phase transformation field?

COMSOL with Simulink Error: ARM64(M2) is not suitable for the _fmu file

Wed, 26 Feb 2025 13:10:57 +0000

When I use the COMSOL with Simulink, I find the matlab cannot run at all. And matlab gives me the error information (attashed in the last). The basic means is that the "fmu" file is incompatible architecture (have 'arm64', need 'x86_64'). So, does the comsol have optimize the error? What I am currently use is the MATLAB in 2022a version (if I use the MTLAB 2024a, the _fmu file cannot be applied because the simulink cannot find the libcsfmu.dylib file), and the version of COMSOL is 6.2. Thank you for any helpful information about this!!! I have focused on this error many days, please~~~

Error information: Error in supplied FMU: Unable to load dynamic library '/Users/wenkii/Library/Preferences/COMSOL/v62/llsimulink/slprj/_fmu/99b6e6501aca8335f57f836b8e97af11/transient/binaries/darwin64/libcsfmu.dylib': dlopen(/Users/wenkii/Library/Preferences/COMSOL/v62/llsimulink/slprj/_fmu/99b6e6501aca8335f57f836b8e97af11/transient/binaries/darwin64/libcsfmu.dylib, 0x0006): tried: '/Users/wenkii/Library/Preferences/COMSOL/v62/llsimulink/slprj/_fmu/99b6e6501aca8335f57f836b8e97af11/transient/binaries/darwin64/libcsfmu.dylib' (mach-o file, but is an incompatible architecture (have 'arm64', need 'x86_64')), '/System/Volumes/Preboot/Cryptexes/OS/Users/wenkii/Library/Preferences/COMSOL/v62/llsimulink/slprj/_fmu/99b6e6501aca8335f57f836b8e97af11/transient/binaries/darwin64/libcsfmu.dylib' (no such file), '/Users/wenkii/Library/Preferences/COMSOL/v62/llsimulink/slprj/_fmu/99b6e6501aca8335f57f836b8e97af11/transient/binaries/darwin64/libcsfmu.dylib' (mach-o file, but is an incompatible architecture (have 'arm64', need 'x86_64')). For more information, see the FMU troubleshooting documentation.

Issues with resuming time-domain simulation due to incomplete data export

Wed, 26 Feb 2025 11:53:05 +0000

Hello

I am currently running a time-domain simulation on a large model, which requires significant disk space to store the entire solution. To manage storage efficiently, I am using the "Store in output" feature to export only the relevant parts of the geometry. However, the simulation's runtime exceeds the job time limits on our cluster, which prevents me from resuming the calculations using the -recover -continue options in batch mode. This is due to the lack of saved data in regions that were not included in the output, which causes issues with providing consistent initial conditions for restart.

I would appreciate any suggestions or solutions to resolve this issue.

Edit: One possible idea that I'm not sure how to implement, is to find a way to store the full solution for the last time step only withing the recovery file. Once a new time step is computed, the previous recovery full solution is replaced by the new one.

Help with domain selection in transport of diluted species physics study

Tue, 25 Feb 2025 22:20:51 +0000

I am looking to do a transport of diluted species study on a test bed that holds two different materials. Material A is in a specific place with a specific concentration and I want to study how it diffuses into the rest of the test bed that is Material B. To do this analysis I am looking to use the transport of diluted species physics but am getting stuck.

I assume that I need to select both domains of Material A and Material B initially in the domain selection. But, when I try to select initial values for Material A, it sees the test bed as one domain rather than the two domains I selected. In the geometry and material selection it registers them as different domains and it is set to form as an assembly.

Please let me know what I should do or if there is another approach I can try.