Latest Discussions - COMSOL Forums

How to excite an HTS coil with current?

Thu, 29 May 2025 14:25:50 +0000

Hello, i am learning to use COMSOL, and i wanted to know how i can excite a superconducting HTS coil with a DC current. I started to learn with a regular copper coil, using Magnetic Fields module, mf, where i can use the coil domain, defining there the turns, and the current excitation. Now i wanted to try with an HTS coil, now represented with an homogeneous bulk of hts tape, with different turns. For this I am using the Magnetic Fields formulation, H formulation, mfh. Using the Farady's Law domain for the hts, where i define the power law for the non linear resistivity. My question is, using this module how can i excite this coil with a current, for a stationary study? And for future frequency domain studies, is it possible to connect to an electrical circuit? Like with the coil domain, from mf?

Thanks, Vitor

Study inside Study

Thu, 29 May 2025 01:36:18 +0000

Hi everyone, I need some help with a multiphysics simulation in COMSOL. I'm working on a model that involves two main studies:

-A time-dependent study, where certain material properties (permittivity and conductivity) evolve over time according to a time-dependent variable.

-A frequency domain study, where I want to evaluate the capacitance of the system based on the state of the material at each time step from the time-dependent study.

My goal is to: Run a time-dependent simulation (e.g., from 0 to 6000 hours, with 1000-hour intervals). At each time step, perform a frequency-domain analysis (using a fixed excitation frequency). Extract the capacitance at a specific point in the excitation cycle (e.g., the peak of a square wave).

However, I'm running into issues: The material properties used in the frequency domain study seem to stay fixed rather than update based on the time-dependent solution. As a result, the capacitance result doesn’t change between time steps. I tried using the “Values of variables not solved for” field to specify the correct times, but I get errors like "parameter mismatch" or the solver just doesn't progress.

My question: How can I configure COMSOL so that the frequency domain study is evaluated at each time step of the time-dependent study, using the updated material properties from that time?

Thanks in advance for any tips!

High-Pressure Hydrogen Flow Modeling

Wed, 28 May 2025 13:29:16 +0000

Hello everyone,

I’m new to COMSOL and would appreciate some guidance. I want to model the flow of high-pressure hydrogen through a pipe and valve. Specifically, I’m interested in understanding how the pressure affects the valves and bends in the pipe, and how the temperature and pressure change throughout the flow.

Could anyone guide me on the best possible approach to model this in detail? Also, are there any blogs or videos you would recommend to help me understand this better?

Separating Substrate and Ground Changes S11 Significantly

Wed, 28 May 2025 10:56:10 +0000

Hey guys,

I'm working on simulating an antenna with a ground plane (green). Initially, the ground was modeled as part of the substrate, but since I want to study different ground geometries, I split them into two separate blocks: one for the substrate and another for the ground.

However, even before modifying the geometry, I'm seeing a significant difference in results. For instance, the S11 parameter shifts from -64 dB (combined model) to -23 dB (split model).

I've tried several things to resolve this, including:

Using Union, Compose, Ignore interior faces, and Merge entities

Adding a boundary layer in the mesh (but it takes ~2 hours just to generate the mesh)

None of these have solved the issue so far. Has anyone dealt with something similar? Is there a better way to replicate a layer?

Any insights would be greatly appreciated!

Integral /surface of a Transmission plot

Wed, 28 May 2025 09:49:10 +0000

Hi everyone

I am doing some calculation on some structures to measure transmission. I am doing a parametric sweep changing the geometry and I end up with many plots of wavelength vs Transmission from mid to long wave infrared 3-14 um.

Is there a way to do the integral of the plots (each plot individually) so I can get the surface below the plot? I want to get a single value that can give me an indication of the total transmission?

Thank you

Young's modulus calculation

Wed, 28 May 2025 01:34:48 +0000

How anyone help me how to calculate Stress, Strain and Young's modulus in graphene

COMSOL version 6.3 Update 2 is available

Tue, 27 May 2025 17:47:33 +0000

Update 2 for COMSOL software version 6.3 has been released. It brings a number of significant performance and stability improvements. Users with an on-subscription license can download the update from this link.

Time Domain: Results mismatch when adding additional range

Tue, 27 May 2025 12:51:11 +0000

Dear Network,

I have a simple time transient thermal analysis (only heat conduction) that runs well. However when adding an additional range I observe that the results before that range (temporarily wise) are changing what is very strange.

In a nutshell : I have results A untill 10ms achieved using rangeA

I run a new simulation with an additional range called rangeB.

So my full simulation time step for that new simulation is rangeA and rangeB like rangeA = 0,0,1,0,001 and then rangeB = 0,001, 1, 10 (this is an example not real values)

Values (especially peak values) with the new simulation are strongly different compared to the initial values from the first simulation. I tried user controlled mesh and a lot of things but nothing change. Do you have any advice ?

Maybe the fact that resolution in rangeA is quite different than resolution=timestep in rangeB ?

Many thanks

Guillaume

Positive S11 parameters when modelling Loop antenna

Tue, 27 May 2025 12:32:44 +0000

I am trying to model a circular loop antenna as part of learning COMSOL. For some reason no matter what parameters i change, i end up getting positive S11 parameter values.

I have tried the impedance boundary, scattering boundary, lumped port, and surface current density condition.

Am i missing any boundary condition, or other parameters?

Metanation of CO2

Mon, 26 May 2025 20:10:01 +0000

Hi, always I run the program, always I have the same convertion of CO2 even when I change the operation conditions (Temperature, pressure and Flux), I don't know where is my problem, I tried to change everything but maybe I don't see something, so someone who can help.

The interaction between superconducting block pulsed magnetization and permanent magnets.

Tue, 27 May 2025 01:17:39 +0000

Hi,everyone The first step of the model I am doing is to pulse magnetization of the superconducting block, the second part is to use the magnetized superconducting block to interact with the permanent magnet, the first step has been made, and the second part of the operation result always has the wrong number of degrees of freedom at the linearization point, can you guide me? Thank you.

Power transfer between two coils

Mon, 26 May 2025 15:29:27 +0000

Hello,

I am trying to quantify the power transfer between two coils. I added lumped ports to both of these coils, and only turned wave excitation on for one of them. I am trying to get the S21 parameter, but it is always negative, and has a magnitude greater than 1. Does anyone know why I am getting these results, or how I could go about finding my power transfer efficiency?

Thanks

Periodic injection

Mon, 26 May 2025 12:15:02 +0000

Hi，all I want to use Comsol to simulate the effect of different contact angles in micropores on two-phase flow. In the first stage, I simulate the injection of hydrogen into the micropores of saturated brine to displace the brine and calculate the phase volume after injection. In the second stage, based on the previous calculation, I inject brine to simulate the extraction process of hydrogen from the pores. How can I complete these two stages of modeling?

Adding Friction in Certain Direction (Charged Particle Tracing)

Mon, 26 May 2025 05:32:11 +0000

Hi there,

I'm trying to simulate ion movement in electromagnetic fields using Charged Particle Tracing module. The ion is subject to two kinds of forces:

DC and RF fields, generated by the electrodes
Laser cooling forces, which can be approximated as friction

Due to experimental limitations, the laser cooling force can only be applied in a certain direction. However, it seems that I can only add homogeneous friction (using the collision model) in Charged Particle Tracing module.

Now I want to add a friction force =-βvx, where vx being the ion's velocity in x direction, and β is the proportionality constant. Is there a way to do that?

Thanks a lot in advance!

Prism based SPR biosensor

Sun, 25 May 2025 23:34:40 +0000

I have designed an SPR biosensor ( prism-Ag-dielectric-sensing medium). I have selected port condition in TM polarization. But light is not passing through the layers. what should I do?? please help me. this is my first account I don't know how to attach any pictures.

output angular velocity in post processing

Sun, 25 May 2025 09:11:26 +0000

When simulating a round object that is rotating or rolling, how to output the angular velocity in post processing?

Cohesive Elements

Sat, 24 May 2025 19:10:45 +0000

Hey, I am trying to do simulation of Li-ion battery degradation. I have performed diffusion analysis but to see the crack propagation, I have to use the cohesive elements. Does anyone know how to do that? I have been searching online but its not helpful. Thanks in advance.

Pulsed electric current as an input to Comsol

Sat, 24 May 2025 18:48:47 +0000

Hi there,

Does anybody know how to create an input (BC or parameter in the PDE Coefficient Form) for the pulsed electric current?

Thanks, Valeriy

How to model weld lines connecting two plates

Sat, 24 May 2025 12:45:42 +0000

Hi there,

I'm trying to simulate the stress that is exerted on weld lines that join two plates together. Now how do I model the weld lines? Do I create a geometry for them or is there a way to connect surfaces only in defined areas?

Thanks a lot in advance

Inconsistent Simulation Results When Narrowing Frequency Range (Electromagnetic Simulation)

Wed, 21 May 2025 13:56:33 +0000

Hello everyone,

I'm currently running an electromagnetic simulation in COMSOL, and I'm encountering an unexpected issue regarding the frequency sweep.

When I simulate over the full frequency range from 0.3 GHz to 3 GHz, the results behave as expected — including the appearance of a resonance peak around 0.685 GHz.

However, when I narrow the frequency range to focus specifically on this peak, for example from 0.68 GHz to 0.71 GHz, the simulation produces different values for S-parameters, and the peak response does not exactly match the one seen in the full-range sweep.

I'm using the same physics settings, mesh, and solver configurations in both cases. Has anyone experienced similar behavior? Could this be related to frequency-dependent boundary conditions, mesh resolution, or solver settings that are sensitive to the sweep range?

Any insights or suggestions would be greatly appreciated!

Best regards, Ricarte Ferreira