Latest Discussions - COMSOL Forums

Adding a DC bias to an AC signal - Electrostatics

Thu, 03 Oct 2024 13:13:14 +0000

Hello,

For the sake of my question, lets say I am attempting to calculate an electric field in a very simple geometry (3 plates of equal spacing. All I am given is that the plates are 3kV apart (+3 on the top, 0 in the middle, -3 on the bottom), and they are riding on a 10kV RMS AC signal.

I have attempted using a boundary electrical potential condition with a harmonic perturbation, but I have little confidence in the correctness of my approach.

For clarity: I am asking the best way to apply 10kV RMS AC signal +/- 3kV DC offset to a geometry.

I am using version 6.1, and the AC/DC module.

SAC and STL

Thu, 03 Oct 2024 11:43:54 +0000

Am doing my research in acoustics. I need to know what multiphysics and boundary conditions to be used while doing simulation of a micro-perforated panel to find its sound absorption coefficient (SAC) and sound transmission loss (STL) in an impedance tube in COMSOL .

Heat and mass transfer- Thermal stresses?

Thu, 03 Oct 2024 10:31:33 +0000

Hello COMSOL Community,

I am looking to model a process where water flows through a narrow channel within porous media, contributing to the cooling effect while also penetrating the porous walls. I have included a schematic of the problem below for reference.

My primary goals are to determine the temperature profile and assess the resulting thermal stresses within the medium. I would greatly appreciate any guidance or suggestions on how to effectively simulate this process.

Thank you in advance for your assistance!

Added mass, Mass type

Thu, 03 Oct 2024 09:28:03 +0000

Hello. I'm confused about something in the process of using COMSOL, so I have a question.

I have a question about 'added mass' in Solid Mechanics. When I add an 'added mass', I select the 'Mass Type'. Also, in 'Boundary Selection', I select some geometries(or boundaries) to which the added mass will be added . When I set the Mass type to Total mass, I have to enter the value for 'kg'.

What I'm wondering is, if I select a total of 4 geometries in the boundary selection and enter a total mass of 10 kg, is the mass of 10 kg added to each of the 4 geometries, or is it entered so that the total sum of the mass for the 4 geometries is 10 kg?

RF MEMS switch insertion loss, isolation and return loss

Thu, 03 Oct 2024 04:37:51 +0000

How to find the RF parameters like insertion loss, isolation and return loss for MEMS switch using COMSOL

Small air gap boundary condition

Wed, 02 Oct 2024 16:49:21 +0000

I am simulating some induced eddy currents in a copper plate suspended above an alternating magnetic dipole (10 kHz). I want to split the copper plate into two halves and apply a boundary condition (or equivalent) between the two halves which simulates the copper plates not quite touching and prevents current from flowing across/normal to the boundary condition.

I have had success by creating a physical air gap between the plates (you can see the thin domain along the center of the plate which I have been setting as air material), but not by setting a boundary condition.

In my model at the moment I have a 'Magnetic Insulation 2' boundary condition which I am hoping to replace for another which will give me the desired properties.

What is best practice for simulating small air gaps like this specifically to prevent eddy current flow?

Issues with remeshing

Tue, 01 Oct 2024 19:36:04 +0000

Hello, I am having issues with the automatic remesh feature, with the error message:

The following feature has encountered a problem: - Feature: Automatic Remeshing 1 (sol1/t1/ar1) Nonlinear solver did not converge. Maximum number of Newton iterations reached. Time: 1.9287941136439875 s.

To reproduce the problem, I took the water_balloon.mph case and added the automatic remeshing node with the requirement that it remeshes every 0.1 sec: range(0,0.1,15). What happens is that there are a few successfull remeshing until I get the error message. Changing "Consistent innitialization" to "on" anticipates the failure to 0.69 s. Without remeshing at all, the default case, the simulation continues to 6.5896 s.

The remeshing instruction is unnecessary for this specific case, but it helps me reproducing an issue that I am observing on a case problem (that I cannot share) where the mesh deforms considerably and remeshing seems to be the only way to continue the simulation.

It's understandable that remeshing might fail, but I wonder if there are ways to mitigate this effect. Maybe a special type of mesh is not prone to this issue?

Thank you

Solver error only at lower frequencies

Tue, 01 Oct 2024 15:11:20 +0000

I am looking at a magnetic fields study in which I want to produce some eddy currents in a copper plate above an alternating magnetic dipole.

I have attached the .mph file

When I run a frequency domain study at 10,000 Hz everything seems to solve fine. When I reduce the frequency to say 100 Hz or 1000 Hz and press the Compute button, I get the following error:

Feature Stationary Solver 1 (sol1/s1) Failed to find a solution. Matrix has zero on diagonal. Returned solution is not converged. Bot all parameter steps returned.

Can anyone see what the cause is? Thankyou in advance for any input.

Undefined material property 'murbnd' required by Transition Boundary Condition

Tue, 01 Oct 2024 15:02:35 +0000

I have problem with defining material property which I have face this error message: "Undefined material property 'murbnd' required by Transition Boundary Condition" and I uploaded my file here and I really don't know where is my problem!

How to find calculate Elastic Strain Energy Density

Mon, 30 Sep 2024 18:28:13 +0000

hello

I'm currently doing a Eigenfrequency Prestressed study of the system (attached is the Mph file)

I want to find out Elastic Strain Energy Density of 10 mode shapes( attached is a image of the equation)

does Comsol provide Elastic Strain Energy Density or do i need to manually do a volume intergal?

thank you!

How To add derivative boundary condition

Mon, 30 Sep 2024 17:51:44 +0000

I am working on a project in which I want to apply the derivative of Magnetic scalar potential (Vm) at the topmost and bottommost boundary of my rectangular(2D) domain . I don't know the value of Vm but I know the value of Derivative of Vm with respect to vertical axis(=y). Help me how to apply it. I am using comsol 6.2.

How to model laser induced convective flows using COMSOL?

Mon, 30 Sep 2024 14:26:24 +0000

I want to create a model where a laser beam is used to heat up a thin layer (5nm) of gold. It would be required to consider interactions of the laser with both fluid and solid materials as the solid object with the gold layer is submerged in a small micro well. Please refer to the attached document to get an idea about the model.

At this point I believe using "Radiative Beam in Absorbing Media" in COMSOL 6.2 is a good option. Any suggestions would be appreciated.

green tab for computing progress in the progress window is missing

Mon, 30 Sep 2024 11:02:31 +0000

green tab for computing progress in the progress window is missing. can anyone help?

How to limit maximum temperature in heat transfer in solids

Mon, 30 Sep 2024 09:27:32 +0000

Hello. I'm simulating microwave heating.

I'm simulating SiC susceptor heating situation with microwave heating, heat transfer in solids.

SiC susceptor I use melts when the temperature reaches over 1200 degree but the temperature distribution of simulation results show SiC susceptor reaching over 2000 degree.

Is there any method to limit maximum temperature of material? I appreciate any advice. Thank you.

Interpreting electric field distribution in metallic chamber

Sun, 29 Sep 2024 12:39:08 +0000

Hello. I'm simulating microwave furnace consists of waveguide, 2.45Ghz 3kw magnetron, metallic chamber.

I'm am troubling interpreting the result. According to my waveguide mode analysis, I found that microwave in the rectangular waveguide propagates with TE10 mode.(You can see the picture below)

But when I combined waveguide with metallic chamber, I could see that there are 2 hot spots in the microwave chamber and I don't understand why it happens.

I think that the result should show electric field concentrated on the middle.

If you have any idea why it shows result like the picture I posted, I would appreciate your advice.
If you have no idea why it happens, is there any recommendation for analysis tool that helps me to understand the result?

Thank you a lot.

Changing the axis of symmetry in 2D domains

Sun, 29 Sep 2024 10:54:37 +0000

The below post is related to an archived discussion

Hello, from the archived discussion above, I understand that changing the axis of symmetry was not possible 5 years back. I would like to know if it is possible now in version 6.1, and if so, how?

Otherwise, my query is:

I want to create a cylindrical domain where the axis of symmetry is along the z-axis, and not in radial direction. How can I do this?

Thanks in advance!

Comsol and Neural Network Integration

Sun, 29 Sep 2024 06:57:13 +0000

Can anyone suggest me helpful guides/resources regarding replacing the solver in COMSOL with Neural Network?

Weight loss detection in Coupon by COMSOL Multiphysics

Sat, 28 Sep 2024 16:58:24 +0000

Dear Sir..

I am MSc student, my project requires knowing the weight loss in a carbon steel coupon, that is immersed in a mixture of water and a corrosion inhibitor (the difference in coupon’s weight before and after the experiment) by fixing the following factors (concentration of the corrosion inhibitor, temperature, velocity of mixture, PH, and time). What are the detailed steps to represent this by using COMSOL Multi-physics ?

I will be so appreciate for your help

Best Regards

Out of memory during LU factorization

Fri, 27 Sep 2024 15:47:01 +0000

Could you help to understand what is wrong in my model? I get not converged solution error. You can find the model in attachment

Permittivity, permeability and conductivity testing of fine alloy powder

Fri, 27 Sep 2024 13:03:28 +0000

I am trying to find a laboratory or research institution (anywhere globally) where we can have permittivity, permeability and conductivity testing undertaken on a very fine dry crystalline alloy powder. Predominantly it is FeSiTi phase with secondary Ti(Fe)C phase and minor (Fe,Ti,Si)Ox phases present. The powder is extremely fine with a D50 of 6-7micron and D99 of approx. 15micron. Most metallurgists we have approached, especially in the powder metallurgy arena have suggested that to conduct the tests they expect the powder would likely need to be formed/compacted into a compact/pellet or disc to analyze it. We do however not want to engage in compacting, or even sintering of the powder, as our company is focused solely on being a supplier of the powder to other industries. So to test the permittivity, permeability and conductivity characteristics of the powder we would be looking for an institution which can undertake the analysis of the powder and transform it into whatever form best suits their needs to do the evaluations. At this stage we have found some interesting application for the powder in composites, and thus they need to better characterize these attributes. Any suggestion by the forum?